; *** DEBUG FREE NOPED TO FIT ;I2L.ASM MAY-23-98 Version 0.91 ;I2L.ASM 10-MAR-2000 Version 1.02 Richard Ottosen ;XPL0 Interpreter for the Scenix SX Microcontroller ;Copyright (C) 1998,1999,2000 Loren Blaney ; ;Assemble using MPASM. ;;This program executes the I2L code produced by the XPL6 compiler. This ; program is based on code written for the 6502 by: P.J.R. Boyle, Wayne Wall, ; Ted Dunning, Loren Blaney, Larry Fish and Richard Ottosen. ; ;See SXPL.DOC for details about what this program does and how it differs ; from other implementations of I2L. ; ;LICENSE: ;This program is free software; you can redistribute it and/or modify it under ; the terms of the GNU General Public License version 2 as published by the ; Free Software Foundation. ;This program is distributed in the hope that it will be useful, but WITHOUT ; ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS ; FOR A PARTICULAR PURPOSE. See the GNU General Public License for more ; details. ;You should have received a copy of the GNU General Public License along with ; this program (in the file LICENSE.DOC); if not, write to the Free Software ; Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. ; ;You can reach me at: Mail: Loren Blaney ; Email: loren_blaney@idcomm.com 502 Pine Glade Dr. ; Nederland, CO 80466, USA ; ;REVISIONS: ;1.0, MAY-09-98, Released. ;1.01, 22-FEB-2000, Changed the routine name "SWAP" to be "SWAPB" to prevent ; conflicts with SX-Key assembler and removed references to pseudo-ops for ; SXSIM. R.O. ;1.02, 10-MAR-2000, Selected internal oscillator and enabled the watchdog ; timer. Added CLRWDT to SOUND intrinsic and at OPGO label. Assigned ; prescaler set to maximum time to watchdog. R.O. ; ; ;CODING CONVENTIONS: ;Bank 0 is normally selected. This enables access to locations 00-1Fh. ;FSR is not set aside as the stack pointer (unlike in the 14-bit version); ; I2LSP is. I2LSP's bit 4 is undefined until it's used in PUSH or PULL. ;The least significant byte of a multi-byte value is at the lowest address ; (i.e. low byte first), except for the stack where the order is reversed. ;The MODE register is not assumed to be set to 0Fh. ;Location 01 is not assumed to be RTCC or W. The OPTION intrinsic can set ; it either way. ; ;Because of fragmented RAM a distinction is made between logical addresses ; and physical addresses. Logical addresses are continuous and range from ; 00 to 7Fh. Logical addresses 0-Fh correspond to physical addresses 10-1Fh. ; Bit 4 in the physical address is always set. Note that the I/O ports ; (RA, RB, RC) are not mapped into logical addresses. The intrinsics Pout ; and Pin are used to access them. All addresses are logical unless noted ; as physical addresses. ; ;*** PROCESSOR 16C57 ;closest PIC chip RADIX DEC ERRORLEVEL -302, -305 ;bank args are in range; ",F" is the default LIST ST=OFF ;we don't need no stinking symbol table INCLUDE "SXDEFS.INC" ;macro definitions for new instructions, etc. ID 'X','P','L','0',' ',' ',' ',' ' ;***DEVICE EQU PINS18+OSCRC+PAGES4+BANKS8+TURBO+SYNC+STACKX+OPTIONX+BOR40+WATCHDOG DEVICE EQU PINS18+OSC4MHZ+PAGES4+BANKS8+TURBO+SYNC+STACKX+OPTIONX+WATCHDOG+BOR40 ;Miscellaneous ASCII control codes: Bel EQU 07h ;bell LF EQU 0Ah ;line feed FF EQU 0Ch ;form feed CR EQU 0Dh ;carriage return EOF EQU 1Ah ;end of file Esc EQU 1Bh ;escape Sp EQU 20h ;space ;=============================================================================== ; START OF RAM ;=============================================================================== ORG 08h TEMP RES 1 ;very temporary scratch location RegA RES 2 ;16-bit scratch "register" RegX RES 1 ;8-bit scratch "register" I2LPC RES 2 ;interpreter's program counter LOCDISP RES 1 ;base address of local variables ORG 0Fh DISPLY RES 3 ;display vector table: holds base addresses of DISPLY2 EQU DISPLY*2 ; heap variables, one for each (static) level LEVEL RES 1 ;current (static) level (0..2) HP RES 1 ;heap pointer, base of unused variable space I2LSP RES 1 ;interpreter's stack pointer (physical address) REMAIN RES 2 ;remainder from integer divide RERUNF RES 1 ;rerun flag; set by RESTART intrinsic, etc. ERRNO RES 1 ;I2L error number TRAPS RES 2 ;16 flags to enable trapping specific I2L errors NOWDEV EQU TEMP ;current I/O device number (always 0) RegB RES 2 ;16-bit scratch "registers" used by various RegC RES 2 ; routines such as MUL, DIV and DOERROR FLAGS RES 1 ;eight scratch flag bits ORG 30h HEAPLO EQU (($>>1) & 70h) | ($ & 0fh) ;use a logical address instead ; of a physical one to cope with fragmented RAM ;The first two bytes in the heap are used to return integers from functions RES 2 SEED RES 3 ;random number seed (in unused heap space) STACK EQU 0FFh ;stack (PUSH = MOVWF IND DECF FSR) ;=============================================================================== ORG 0 ;START OF ROM ;=============================================================================== ;GOTO and CALL extenders ; ISR FGOTO ISRX ;interrupt vector at location 0 RESET FGOTO RESETX DOERROR FGOTO DOERRORX FETCHA FGOTO FETCHAX ;------------------------------------------------------------------------------- ;Routine to quickly load global and local variables onto the stack. Since this ; is the most common I2L instruction, it is optimized. This is a single-byte ; instruction with the high bit set. The other 7 bits are the offset. Globals ; are indicated by odd offsets, and locals by even offsets. ; FASTLOD BCF RegX,7 ;clear high bit of opcode to get the offset MOVF LOCDISP,W ;get base address of local variables BTFSC RegX,0 ;skip if offset is even (it's a local variable) MOVF DISPLY,W ; else get base address of global variables ADDWF RegX,W ;add offset to get (logical) address in heap OPGOLOD CALL GETVAR ;f variable from heap and put it into RegA OPGOPA MOVF RegA,W ;push RegA, low byte first OPGOPAW CALL PUSH MOVF RegA+1,W ;push RegA high byte OPGOPW CALL PUSH ;fall into dispatch loop... ;=============================================================================== ; MAIN DISPATCH LOOP ;=============================================================================== ; OPGO CLRWDT ;***??? R.O. CALL FETCH ;f opcode at I2LPC and increment I2LPC MOVWF RegX ;save copy of opcode in RegX BTFSC RegX,7 ;skip if MSB (bit 7) is clear GOTO FASTLOD ; else go handle fast global or local load BTFSC RegX,6 ;skip if bit 6 is clear GOTO SSIMOP ; else go handle short, short immediate load ADDWF PC ;jump to routine that handles this opcode ;Opcode Jump Table: Opcode / No. of Bytes / Description GOTO EXTOP ;$00,1, Display error message then go to START GOTO LODOP ;$01,3, Load a variable onto stack GOTO LDXOP ;$02,3, Indexed load a byte variable GOTO STOOP ;$03,3, Store into a variable GOTO STXOP ;$04,3, Indexed store into a byte GOTO CALOP ;$05,4, Call a procedure GOTO RETOP ;$06,1, Return from procedure GOTO JMPOP ;$07,3, Jump GOTO JPCOP ;$08,3, Jump if top-of-stack (TOS) is false (=0) GOTO HPIOP ;$09,2, Increase heap pointer (HP) by argument GOTO ARGOP ;$0A,2, Move arguments from stack to heap GOTO IMMOP ;$0B,3, Load 16-bit immediate value GOTO CMLOP ;$0C,2, Call an intrinsic ('code') routine GOTO ADDOP ;$0D,1, Add GOTO SUBOP ;$0E,1, Subtract GOTO MULOP ;$0F,1, Multiply GOTO DIVOP ;$10,1, Divide GOTO NEGOP ;$11,1, Negate (2's complement) GOTO EQOP ;$12,1, Test for = GOTO NEOP ;$13,1, Test for # GOTO GEOP ;$14,1, Test for >= GOTO GTOP ;$15,1, Test for > GOTO LEOP ;$16,1, Test for <= GOTO LTOP ;$17,1, Test for < GOTO FOROP ;$18,3, 'for' loop control GOTO INCOP ;$19,5, Increment, push & jump ('for' loop) GOTO OROP ;$1A,1, Or GOTO ANDOP ;$1B,1, And GOTO NOTOP ;$1C,1, Not (1's complement) GOTO XOROP ;$1D,1, Exclusive or GOTO DBAOP ;$1E,1, TOS:= NOS + TOS*2 (for arrays) GOTO STDOP ;$1F,1, Store TOS at address in NOS GOTO DBXOP ;$20,1, Load(TOS*2 + NOS) GOTO ADROP ;$21,3, Load address of a variable GOTO LDX2OP ;$22,2, Indexed load global or local byte GOTO BRAOP ;$23,2, Branch to I2L code GOTO SIMOP ;$24,2, Load short (8-bit) immediate value GOTO CJPOP ;$25,3, Case jump GOTO JSROP ;$26,3, Optimized procedure call GOTO RTSOP ;$27,1, Optimized procedure return ;To save space the following code replaces external call and floating point ops ;------------------------------------------------------------------------------- ;$28 ;Routine to pull TOS and discard it. This is used to clean up the stack in ; unusual situations such as a 'return' inside a 'for' loop. ; DRPOP CALL PULLA ;$28,1, Discard TOS GOTO OPGO ;($29) ;------------------------------------------------------------------------------- ;Pull into RegB and add it to RegA ; PBDADD CALL PULLB ;($2A) ;fall into DADD... ;------------------------------------------------------------------------------- ;RegA:= RegA + RegB. ; DADD MOVF RegB,W ;($2B) add low bytes ADDWF RegA ;($2C) MOVF RegB+1,W ;($2D) get ready to add high bytes BTFSC STATUS,C ;($2E) skip if there was no carry into high byte INCFSZ RegB+1,W ;($2F) else add in carry; if zero then high byte ADDWF RegA+1 ;($30) doesn't change and carry is still set RETP ;($31) i.e. carry is correct ;------------------------------------------------------------------------------- ;Compare RegA to RegB by subtracting (RegB+$8000) from (RegA+$8000). The $8000 ; offset allows an unsigned compare to be used. If the carry flag is set then ; RegA is >= RegB. This works for the entire range of values so, for example, ; -30000 is correctly determined to be smaller than +30000. RegA and RegB are ; changed. ; DCMP MOVLW 80h ;($32) add $8000 to avoid discontinuity between XORWF RegA+1 ;($33) -1 and 0 XORWF RegB+1 ;($34) fall into DSUB... ;------------------------------------------------------------------------------- ;RegA:= RegA - RegB (with correct carry). Returns with RegB+1 in W. ; DSUB MOVF RegB,W ;($35) subtract low bytes SUBWF RegA ;($36) MOVF RegB+1,W ;($37) get ready to subtract high bytes BTFSS STATUS,C ;($38) skip if there's no borrow from high byte INCFSZ RegB+1,W ;($39) else increase amount to subtract by 1 SUBWF RegA+1 ;($3A) if it's 0 then high byte doesn't change, RETP ;($3B) nor does carry ;------------------------------------------------------------------------------- ;(Resume Opcode Jump Table) GOTO STO2OP ;$3C,2, Store into global or local variable GOTO STX2OP ;$3D,2, Indexed store into global or local ;------------------------------------------------------------------------------- ;$3E ;Shift left. TOS:= NOS << TOS ; Only the low byte of the shift count is used. It should normally be < 16. ; LSLOP NOP ;$3E,1, Shift left (the NOP is necessary) ; fall into LSROP... ;------------------------------------------------------------------------------- ;$3F ;Shift right. TOS:= NOS >> TOS ; LSROP CALL PULLB ;$3F,1; TOS into RegB, low byte of RegB is in W BTFSC STATUS,Z ; and the status is set accordingly GOTO OPGO ;branch if shifting zero places CALL PULLA ;NOS into RegA LSR20 BCF STATUS,C ;clear carry bit for shifting BTFSS RegX,0 ;skip if odd numbered opcode (LSROP) GOTO LSR30 ; else branch to shift left RRF RegA+1 ;shift right --> RRF RegA GOTO LSR40 LSR30 RLF RegA ;shift left <-- RLF RegA+1 LSR40 DECFSZ RegB ;loop for the number of places in RegB (=TOS) GOTO LSR20 GOTO OPGOPA ;go push RegA ;=============================================================================== ; SUBROUTINES ;=============================================================================== ;Return the heap address of a variable. This fetches an instruction's level and ; offset and returns the corresponding heap address in W. ; HEAPADR CALL FETCH ;fetch level (times 2) MOVWF FSR MOVLW DISPLY2 ;add base of display vector table (times 2) ADDWF FSR RRF FSR ;undo times 2 (carry is clear because of ADDWF) CALL FETCH ;get offset (does not change FSR) ADDWF IND,W ;add it to base address from table to get addr RETP ; in heap ;------------------------------------------------------------------------------- ;Return the heap address of a local or global variable. This fetches an ; instruction's offset and returns the corresponding heap address in W. ; Bank 0 is no longer selected. ; HEAPADRX CALL FETCH ;fetch offset MOVWF FSR ;BANK 0 IS NO LONGER SELECTED MOVF LOCDISP,W ;get base address for local level BTFSC FSR,0 ;skip if offset is even (it's a local variable) MOVF DISPLY,W ; else get base address of global variables ADDWF FSR,W ;add offset to get heap address RETP ;------------------------------------------------------------------------------- ;Convert the logical address in W into a physical address in FSR (to cope with ; fragmented RAM). Bank 0 is no longer selected. ; LOGPHYS MOVWF FSR ;BANK 0 IS NO LONGER SELECTED ANDLW 0F0h ;shift the high nibble left ADDWF FSR ;(bit 4 will be set later) BSF FSR,4 ;make sure FSR is pointing to high half of bank RETP ;------------------------------------------------------------------------------- ;Get the variable pointed to by W and put it into RegA. ; GETVAR CALL LOGPHYS ;convert logical address to physical address MOVF IND,W ;fetch low byte MOVWF RegA INCF FSR BSF FSR,4 ;make sure FSR is pointing to high half of bank MOVF IND,W ;fetch high byte MOVWF RegA+1 GOTO PULL90 ;restore access to bank 0 and return ;------------------------------------------------------------------------------- ;Fetch the I2L code byte pointed to by I2LPC and then bump I2LPC. (I2LPC++) -> W ; FSR is not changed. ; FETCH BTFSC I2LPC+1,3 ;skip if fetching from below address 800h GOTO FET50 ; else go fetch two nibbles MOVF I2LPC+1,W ;fetch byte at I2LPC MOVWM MOVF I2LPC,W IREAD ;return byte in W INCFSZ I2LPC ;increment interpreter's program counter RETP ;most of the time it returns from here INCF I2LPC+1 ;increment high byte BTFSS I2LPC+1,3 ;skip if 800h--ignore reset vector at 7FFh RETP ; return DECF I2LPC ;convert 800h back to 7FFh DECF I2LPC+1 ;When fetching at or above address 7FFh, the location to actually fetch from is: ; = (I2LPC - 7FFh)*2 + PROGLO ; = (I2LPC - (800h-1))*2 + PROGLO ; = 2*I2LPC - 1000h + 2 + PROGLO Since 1000h is over the top, it has no effect ; = 2*I2LPC + PROGLO + 2 FET50 RLF I2LPC,W ;RegB:= 2*I2LPC MOVWF RegB RLF I2LPC+1,W FCALL FETCOM INCFSZ I2LPC ;increment interpreter's program counter RETP ; most of the time it returns from here INCF I2LPC+1 ;increment high byte RETP ;return ;------------------------------------------------------------------------------- ;Check for memory overflow. If HP > I2LSP then I2L error # 2: Out of memory. ; CHKMEM MOVF HP,W ;convert logical address in HP to physical ANDLW 0F0h ; address in W, except that bit 4 is clear ADDWF HP,W BCF I2LSP,4 ;compare to similar physical address in I2LSP SUBWF I2LSP,W ;I2LSP - HP MOVLW 2 ;error 2 BTFSS STATUS,C ;skip if no overflow GOTO DOERROR ; else flag error and return RETP ;return with no error ;------------------------------------------------------------------------------- ;Move arguments from stack to heap. The number of bytes of arguments to move is ; in the W register. The location in the heap is pointed to by the heap pointer ; (HP). RegX, and RegA are changed. ; ;Example showing how 2 arguments (4 bytes) are passed. FROG(NOS, TOS); ; ; Initial STACK ---> HEAP ; I2LSP -->| | | | ; +----------+ +----------+ ; 1 | TOS high | HP -->| NOS low | ; +----------+ +----------+ ; 2 | TOS low | | NOS high | ; +----------+ +----------+ ; 3 | NOS high | | TOS low | ; +----------+ +----------+ ; 4 | NOS low |<-- Final I2LSP | TOS high | ; +----------+ +----------+ ; <-- Initial RegA ; MOVARGS MOVWF RegX ;save byte count ADDWF HP,W ;add base address (HP) to get pointer into heap MOVWF RegA ;save this pointer MOV10 CALL PULL ;pull TOS byte from stack MOVWF RegA+1 ;save it temporarily in high byte of RegA DECF RegA ;decrement pointer to heap MOVF RegA,W CALL LOGPHYS ;convert logical address to physical address MOVF RegA+1,W ;store TOS byte into heap MOVWF IND BANKX 0 ;restore access to bank 0 (PULL needs it) DECFSZ RegX ;loop for the specified number of bytes GOTO MOV10 RETP ;------------------------------------------------------------------------------- ;Pull the 16-bit value in TOS into RegA. Returns with copy of RegA in W. ; PULLA CALL PULL ;high byte MOVWF RegA+1 CALL PULL ;low byte MOVWF RegA RETP ;------------------------------------------------------------------------------- ;Pull the 16-bit value in TOS into RegB. Returns with copy of RegB in W. ; PULLB CALL PULL ;high byte MOVWF RegB+1 CALL PULL ;low byte MOVWF RegB RETP ;------------------------------------------------------------------------------- ;Pull the 16-bit value in TOS into RegC. Returns with copy of RegC in W. ; PULLC CALL PULL ;high byte MOVWF RegC+1 CALL PULL ;low byte MOVWF RegC RETP ;------------------------------------------------------------------------------- ;Pull the 16-bit value in TOS into I2LPC. Returns with copy of I2LPC in W. ; PULLPC CALL PULL ;high byte MOVWF I2LPC+1 CALL PULL ;low byte MOVWF I2LPC RETP ;------------------------------------------------------------------------------- ;Pull a byte from the stack and return it in W with its correct Z status. ; PULL INCF I2LSP ;increment stack pointer BSF I2LSP,4 ;make sure it's in the high half of the bank MOVF I2LSP,W ;set FSR as the stack pointer MOVWF FSR MOVF IND,W ;get byte from stack and set Z status PULL90 BANKX 0 ;restore access to bank 0 RETP ;------------------------------------------------------------------------------- ;Push byte in W onto the stack (without changing W or carry). ; PUSH MOVWF TEMP ;save W BSF I2LSP,4 ;make sure it's in the high half of the bank MOVF I2LSP,W ;get stack pointer MOVWF FSR MOVF TEMP,W ;store W onto stack MOVWF IND BANKX 0 ;restore access to bank 0 REPUSH BCF I2LSP,4 ;force low half of bank DECF I2LSP ;decrement stack pointer RETP ; (I2LSP is forced to high half of bank later) ;------------------------------------------------------------------------------- ;Subroutine to set up arguments for divide opcode ; DIV100 CALL PULLA ;TOS -> RegA MOVF RegA+1,W ;get sign bit and XORWF FLAGS ;toggle sign flag if its negative ;fall into ABSA... ;------------------------------------------------------------------------------- ;Return the absolute value of RegA. ; ABSA BTFSS RegA+1,7 ;skip if negative and fall into NEGA... RETP ; else return with positive value ;------------------------------------------------------------------------------- ;Negate RegA (two's complement). ; NEGA COMF RegA COMF RegA+1 ;fall into INCA... ;------------------------------------------------------------------------------- ;Increment RegA (without altering W). ; INCA INCFSZ RegA RETP INCF RegA+1 RETP ;=============================================================================== ; ROUTINES TO EXECUTE I2L INSTRUCTIONS ;=============================================================================== ;$00 ;Exit routine. One-byte instruction. Since in this ROM-based environment there ; is nothing to exit back to (such as an operating system), this is an error. ; EXTOP FGOTO ERREXIT ;------------------------------------------------------------------------------- ;$01 ;Routine to fetch a 16-bit variable's value from the heap and push it onto the ; stack. This instruction is usually replaced by the fast global or local load ; (FASTLOD), but when the variable's level is neither global or local (when it's ; intermediate), this routine is used instead. This is a three-byte instruction: ; 1. The opcode ($01). ; 2. The level in the display vector table for the base address (times 2). ; 3. The offset from that base address to the variable. ; LODOP CALL HEAPADR ;fetch level & offset and point W to heap addr GOTO OPGOLOD ;go get variable from heap and push it on stack ;------------------------------------------------------------------------------- ;$02 ;Routine to push an 8-bit byte onto the stack. This opcode contains the level ; and offset of a variable that points to the base of a character (byte) array. ; An index, which is on the stack, is added to this base address to get the ; address of the byte to push. The byte is pushed as a 16-bit value with its ; high byte zeroed. Three-byte instruction: opcode, level, and offset. ; LDXOP CALL HEAPADR ;fetch level & offset and point W to heap addr LDXOPX CALL GETVAR ;get array base address from heap into RegA CALL PBDADD ;pull index and add it to base of array CALL FETCHA ;fetch (into W) the byte pointed to by RegA LDXPA CLRF RegA+1 ;zero the high byte GOTO OPGOPAW ;go push W & RegA+1 onto the stack ;------------------------------------------------------------------------------- ;$22 ;Compact form of LDX instruction. Used when the variable is global or local. ; Two-byte instruction: opcode, offset. ; LDX2OP CALL HEAPADRX ;get heap address for local or global into W GOTO LDXOPX ;go to common code for LDX instruction ;------------------------------------------------------------------------------- ;$03 ;Routine to store top-of-stack (TOS) into a variable. ; Three-byte instruction: opcode, level, and offset. ; STOOP CALL PULLA ;TOS -> RegA CALL HEAPADR ;fetch level & offset and point W to heap addr ;Store RegA into heap location pointed to by W STOOPX CALL LOGPHYS ;convert logical address into physical address MOVF RegA,W ;get low byte of TOS MOVWF IND ;store it into heap INCF FSR MOVF RegA+1,W ;get high byte BSF FSR,4 ;make sure FSR is pointing to high half of bank STOOPY MOVWF IND ;store it too BANKX 0 ;restore access to bank 0 GOTO OPGO ;go process next instruction ;------------------------------------------------------------------------------- ;$3C ;Compact form of STO instruction. Used when the variable is global or local. ; Two-byte instruction: opcode, offset. ; STO2OP CALL PULLA ;TOS -> RegA CALL HEAPADRX ;get heap address for local or global into W GOTO STOOPX ;go do common code for STO instruction ;------------------------------------------------------------------------------- ;$04 ;Routine to store the value on the stack into an indexed array element. Similar ; to LDX except that the value to store is pushed on the stack after the index ; (i.e: index=NOS, value=TOS). The high byte of the value is ignored and the low ; byte is stored into the heap. Three-byte instruction: opcode, level, offset. ; STXOP CALL HEAPADR ;fetch level & offset and point W to heap addr STXOPX CALL GETVAR ;copy base address of array from heap into RegA INCF I2LSP ;discard high byte CALL PULL ;pull byte to store into array MOVWF RegX ; and save it for now in RegX CALL PBDADD ;pull index and add it to base of array in RegA MOVLW 15 ;make sure high byte is clear, else flag MOVF RegA+1 ; I2L error # 15: Attempt to store into ROM BTFSS STATUS,Z CALL DOERROR MOVF RegA,W ;point FSR to RAM address CALL LOGPHYS ;convert logical address to physical address MOVF RegX,W ;get byte that is to be stored into the array GOTO STOOPY ;go store it and return to OPGO ;------------------------------------------------------------------------------- ;$3D ;Compact form of STX instruction. Used when variable is global or local. ; Two-byte instruction: opcode, offset. ; STX2OP CALL HEAPADRX ;get heap address for local or global into W GOTO STXOPX ;go do common code for STX instruction ;------------------------------------------------------------------------------- ;$05 ;Routine to call a procedure. ; The instruction consists of 4 bytes: ; 1. The opcode. ; 2. The (new) level of the procedure being called (high 3 bits) and the ; number of bytes of arguments to be passed (low 5 bits) (see ARGOP). ; 3. The procedure entry address (low byte). ; 4. The procedure entry address (high byte). ; ; After a procedure call, the stack contains: ; 1. Return address (high byte, low byte). ; 2. Base address of variables (in heap) for the called procedure ; (i.e. value in display vector table at the new level). ; 3. Level of procedure we are calling from. ; ;The entry in the display vector table at the new level is set to the value in ; the heap pointer (HP). This is the base address of any local variables in the ; called procedure. ; CALOP CALL FETCH ;get level and number of arguments MOVWF RegC ;save copy for later ANDLW 1Fh ;get the number of arguments BTFSS STATUS,Z ;skip if no arguments CALL MOVARGS ; else move W bytes of args from stack to heap MOVF LEVEL,W ;push level we are calling from CALL PUSH ;Push the value in the display vector table at the new level SWAPF RegC ;move the level in the high 3 bytes down RRF RegC,W ANDLW 07h MOVWF LEVEL ;set the level for the called procedure MOVLW DISPLY ;index into display vector table ADDWF LEVEL,W MOVWF FSR ;(bank 0 is still selected) MOVF IND,W ;get the base address for the called level MOVWF RegC ;temporarily save base address in RegC MOVF HP,W ;change this entry in the display vector table MOVWF IND ; to the current heap pointer MOVWF LOCDISP ;also save a copy for accessing local variables MOVF RegC,W ;push base address for the called level CALL PUSH ;fall into JSROP... ;------------------------------------------------------------------------------- ;$26 ;Optimized procedure call. Used only if no local variables are present. Since ; the scope is unchanged, this is equivalent to a machine language call. This ; instruction is also used to load the address of a string and then jump over ; the string. Three-byte instruction: opcode, low byte of called address, high ; byte of called address. ; JSROP MOVLW 2 ;push return address (=I2LPC+2) ADDWF I2LPC,W CALL PUSH ;push low byte (and don't disturb carry) CLRF TEMP ;shift carry into W RLF TEMP,W ADDWF I2LPC+1,W ;add high byte CALL PUSH ;push resulting high byte GOTO JMPOP ;go do jump to procedure then return to OPGO ;------------------------------------------------------------------------------- ;$27 ;Optimized procedure return, to match the above call. Pulls the return address ; and puts it into I2LPC. Single-byte instruction. ; RTSOP CALL PULLPC ;pull return address into I2LPC GOTO OPGO ;------------------------------------------------------------------------------- ;$06 ;Routine to return from a procedure. This pops the stuff pushed by CALOP. ; Single-byte instruction. ; RETOP MOVF LOCDISP,W ;restore heap pointer to its location before MOVWF HP ; the call CALL PULLPC ;pull return address into I2LPC CALL PULL ;pull base address of variables we're ret from MOVWF RegA ;save it temporarily in RegA CALL PULL ;pull level for procedure we are returning to MOVWF RegX ;save it temporarily in RegX ;Restore base address entry in display table for level we are returning from MOVLW DISPLY ;index into display vector table for current ADDWF LEVEL,W ; level MOVWF FSR ;(bank 0 is still selected) MOVF RegA,W ;restore base address MOVWF IND MOVF RegX,W ;set LEVEL to the level we are returning to MOVWF LEVEL MOVLW DISPLY ;get base address of variables for this level ADDWF LEVEL,W MOVWF FSR ;(bank 0 is still selected) MOVF IND,W MOVWF LOCDISP ;set pointer for locals we're returning to GOTO OPGO ;------------------------------------------------------------------------------- ;$08 ;The two jump instructions are each three bytes long: ; Opcode. ; Low order of target address. ; High order of target address. ; ;Conditional jump routine. This routine jumps on false, not on true. Note that ; false is zero, and non-zero is true. The result of the last boolean expression ; (typically a compare) is on the stack. Note that the entry point is at JPCOP. ; JPCOPX MOVLW 2 ;move past address to jump to. i.e. don't jump ADDWF I2LPC ;skip two bytes of I2L code BTFSC STATUS,C INCF I2LPC+1 GOTO OPGO JPCOP CALL PULLA ;pull bytes IORWF RegA+1,W ;combine high and low bytes BTFSS STATUS,Z ;skip if false (zero) and fall into JMPOP... GOTO JPCOPX ; else TOS was true so go move past jump address ;------------------------------------------------------------------------------- ;$07 ;Jump instruction. ; JMPOP CALL FETCH ;get low byte of address to jump to MOVWF RegX ;save it temporarily in X CALL FETCH ;get high byte (pointed to by I2LPC) MOVWF I2LPC+1 ;now update I2L's PC MOVF RegX,W MOVWF I2LPC GOTO OPGO ;------------------------------------------------------------------------------- ;$09 ;Routine to increase the heap pointer. This is used to reserve heap space for ; local variables. Two-byte instruction: opcode, number of bytes to reserve. ; HPIOP CALL FETCH ;add the amount to reserve onto HP ADDWF HP CALL CHKMEM ;check for memory overflow (HP > I2LSP) GOTO OPGO ;------------------------------------------------------------------------------- ;$0A ;Routine to move procedure arguments from the stack to the heap. The called ; procedure will then reserve the space with an HPIOP, and the local variables ; thus created will be preset to their appropriate values. Two-byte instruction: ; opcode, number of bytes of arguments. ; ARGOP CALL FETCH ;get number of bytes of arguments CALL MOVARGS ;move W bytes of arguments from stack to heap GOTO OPGO ;------------------------------------------------------------------------------- ;$0B ;Load a 16-bit constant onto the stack. Three-byte instruction: Opcode, low ; byte of constant, high byte of constant. ; TOS:= immediate value. ; IMMOP CALL FETCH ;get low byte of constant MOVWF RegA CALL FETCH ;get high byte MOVWF RegA+1 GOTO OPGOPA ;go push RegA ;=============================================================================== ; ARITHMETIC OPERATIONS ;=============================================================================== ; ;These routines operate on the two items on the top-of-stack (TOS and NOS) and ; return the result in TOS (which replaces NOS). They are all single-byte ; instructions. Items are on the stack as shown. Note that the low byte is ; pushed first. Addresses increase downward. ; ; Initial I2LSP -->| | ; +----------+ ; 1 | TOS high | ; +----------+ ; 2 | TOS low |<-- I2LSP when finished ; +----------+ ; 3 | NOS high | ; +----------+ ; 4 | NOS low | ; +----------+ ; ;------------------------------------------------------------------------------- ;$0D ;Add. TOS:= NOS + TOS. Single-byte instruction. ; ADDOP CALL PULLA ;get TOS into RegA ADDOPX CALL PBDADD ;get NOS into RegB and RegA:= RegA + RegB GOTO OPGOPA ;go push RegA ;------------------------------------------------------------------------------- ;$0E ;Subtract. TOS:= NOS - TOS. Single-byte instruction. ; SUBOP CALL PULLB ;get TOS into RegB CALL PULLA ;get NOS into RegA CALL DSUB ;RegA:= RegA - RegB GOTO OPGOPA ;go push RegA ;------------------------------------------------------------------------------- ;$0F ;16-bit signed multiply. TOS:= NOS * TOS. Single-byte instruction. This uses an ; early-out algorithm. ; ; <-- RegB RegC --> ; + RegA --> ; MULOP CALL PULLC ;get TOS (multiplier) into RegC CALL PULLB ;get NOS (multiplicand) into RegB CLRF RegA ;clear product register CLRF RegA+1 GOTO MUL30 MUL10 CALL DADD ;RegA:= RegA + RegB BCF STATUS,C MUL20 RLF RegB ;shift multiplicand left <-- B RLF RegB+1 MUL30 BCF STATUS,C ;clear carry (don't shift in garbage) RRF RegC+1 ;shift least significant bit of multiplier RRF RegC ; into carry BTFSC STATUS,C ;skip if bit was a 0 GOTO MUL10 ; else it was a 1--go add B to A MOVF RegC,W ;are there any more 1 bits in C? IORWF RegC+1,W BTFSS STATUS,Z ;skip if not--all done GOTO MUL20 ; else loop back skipping add (carry is clear) GOTO OPGOPA ;go return and push product onto the stack ;------------------------------------------------------------------------------- ;$10 ;16-bit signed divide. TOS:= NOS / TOS. Single-byte instruction. ; DIVOP CLRF FLAGS ;bit 7 is used to determine sign of quotient CALL DIV100 ;get TOS and handle sign FCALL DMOVAB ;copy RegA to RegB IORWF RegB,W ;check for divide by 0 MOVLW 1 ;flag I2L error 1 BTFSC STATUS,Z ;skip if no error CALL DOERROR CALL DIV100 ;get NOS and handle sign FCALL DIV ;RegA:= RegA / RegB. BTFSC FLAGS,7 ;skip if quotient should be positive DIV90 CALL NEGA ; otherwise make it negative GOTO OPGOPA ;go push RegA ;------------------------------------------------------------------------------- ;$11 ;Negate. TOS:= -TOS. Single-byte instruction. ; NEGOP CALL PULLA ;get TOS into RegA GOTO DIV90 ;go make it negative and push it ;=============================================================================== ; COMPARE OPERATIONS ;=============================================================================== ; ;Integer compares use the top two items on the stack, and return either a ; true ($FFFF) or false ($0000) value on the stack. They are all one-byte ; instructions. Note that RegX contains the opcode. ; ;------------------------------------------------------------------------------- ;$12 ;Equal? TOS:= NOS = TOS. Single-byte instruction. ; EQOP ;fall into NEOP... ;------------------------------------------------------------------------------- ;$13 ;Not equal? TOS:= NOS # TOS. Single-byte instruction. ; NEOP CALL PULLA ;get TOS into RegA CALL PULLB ;get NOS into RegB (low byte of RegB is in W) SUBWF RegA,W ;compare TOS to NOS BTFSS STATUS,Z ;skip if equal GOTO EQOP3 ; else branch--go return reversed logic MOVF RegB+1,W ;compare high bytes SUBWF RegA+1,W BTFSS STATUS,Z ;skip if equal EQOP3 INCF RegX ;reverse logic by flipping LSB EQOP4 MOVLW 0 ;push either a true or false value depending BTFSS RegX,0 ; on logic MOVLW 0FFh ;use 'true' value PUSHW2 CALL PUSH ;push value in W twice and return GOTO OPGOPW ;go push W ;------------------------------------------------------------------------------- ;$17 ;Less than? TOS:= NOS < TOS. Single-byte instruction. ; LTOP ;fall into GEOP... ;------------------------------------------------------------------------------- ;$14 ;Greater than or equal? TOS:= NOS >= TOS. Single-byte instruction. ; GEOP CALL PULLB ;get TOS into RegB CALL PULLA ;get NOS into RegA GEOP2 CALL DCMP ;compare NOS to TOS BTFSS STATUS,C ;skip if NOS >= TOS GOTO EQOP3 ; else branch--go reverse logic GOTO EQOP4 ;go return unreversed logic ;------------------------------------------------------------------------------- ;$15 ;Greater than? TOS:= NOS > TOS. Single-byte instruction. ; GTOP ;fall into LEOP... ;------------------------------------------------------------------------------- ;$16 ;Less than or equal? TOS:= NOS <= TOS. Single-byte instruction. ; LEOP CALL PULLA ;get TOS into RegA CALL PULLB ;get NOS into RegB GOTO GEOP2 ;go compare TOS to NOS ;=============================================================================== ; FOR-LOOP CONTROL ;=============================================================================== ;$19 ;Routine to increment a variable's value. Five-byte instruction: opcode, level, ; offset, and two bytes for the jump address to continue the 'for' loop. ; INCOP CALL HEAPADR ;fetch level & offset and point W to heap addr CALL LOGPHYS ;convert logical address to physical address INCF IND ;increment low byte of 'for' control variable MOVF IND,W ;and save a copy MOVWF RegA INCFSZ FSR ;increment stack pointer without changing Z stat BSF FSR,4 ;make sure FSR is pointing to high half of bank BTFSC STATUS,Z ;skip if no carry into high byte of variable INCF IND ; otherwise increment high byte of variable MOVF IND,W ;save a copy MOVWF RegA+1 BANKX 0 ;restore access to bank 0 MOVF RegA,W ;push RegA, low byte first CALL PUSH MOVF RegA+1,W ;push RegA high byte CALL PUSH GOTO JMPOP ;go jump to top of 'for' loop ;------------------------------------------------------------------------------- ;$18 ;This routine handles the test and branch of the 'for' loop. The stack contains ; the limit (NOS) and a copy of the loop control variable (TOS). They are ; compared and if the loop variable is greater than the limit, the 'FOR' loop is ; finished. In which case this instruction's address is jumped to, and the stack ; is cleaned up. Otherwise, the 'for' loop continues and the I2LPC is advanced ; to the next opcode, leaving the limit value on the stack. Three-byte ; instruction: opcode, low byte of branch address, high byte. ; FOROP CALL PULLB ;pull TOS (= control variable) into RegB CALL PULLA ;pull NOS (= limit) into RegA CALL DCMP ;compare limit to control variable BTFSS STATUS,C ;skip if limit >= control variable GOTO JMPOP ; otherwise go jump out of the 'for' loop CALL REPUSH ;effectively push limit back onto stack CALL REPUSH GOTO JPCOPX ;skip past branch address in opcode so that the ; 'for' loop will continue ;=============================================================================== ; BOOLEAN OPERATIONS ;=============================================================================== ;$1A ;"OR" operation--bitwise on all 16 bits. Single-byte instruction. ; TOS:= NOS ! TOS. ; OROP CALL PULLA ;TOS into RegA CALL PULLB ;NOS into RegB IORWF RegA ;RegA:= RegA ! RegB MOVF RegB+1,W IORWF RegA+1 GOTO OPGOPA ;go push RegA ;------------------------------------------------------------------------------- ;$1B ;"AND" operation--bitwise on all 16 bits. Single-byte instruction. ; TOS:= NOS & TOS. ; ANDOP CALL PULLA ;TOS into RegA CALL PULLB ;NOS into RegB ANDWF RegA ;RegA:= RegA & RegB MOVF RegB+1,W ANDWF RegA+1 GOTO OPGOPA ;go push RegA ;------------------------------------------------------------------------------- ;$1C ;"NOT" complements all sixteen bits. Single-byte instruction. ; TOS:= ~TOS. ; NOTOP CALL PULLA ;TOS into RegA COMF RegA,W ;RegA:= ~RegA (sort of) COMF RegA+1 GOTO OPGOPAW ;go push W & RegA+1 ;------------------------------------------------------------------------------- ;$1D ;"XOR" operation--bitwise on all 16 bits. Single-byte instruction. ; TOS:= NOS | TOS. ; XOROP CALL PULLA ;TOS into RegA CALL PULLB ;NOS into RegB XORWF RegA ;RegA:= RegA | RegB MOVF RegB+1,W XORWF RegA+1 GOTO OPGOPA ;go push RegA ;=============================================================================== ; ARRAY OPERATIONS ;=============================================================================== ;$1E ; TOS:= NOS + TOS*2. Single-byte instruction. ; DBAOP CALL PULLA ;TOS into RegA ADDWF RegA ;RegA:= RegA * 2 RLF RegA+1 GOTO ADDOPX ;go add RegA to NOS and return to OPGO ;------------------------------------------------------------------------------- ;$1F ;Store TOS into address in NOS and pop both. Single-byte instruction. ; STDOP CALL PULLA ;TOS into RegA CALL PULLB ;NOS into RegB MOVLW 15 ;make sure high byte of address is 0, otherwise MOVF RegB+1 ;flag I2L error # 15: Attempt to store into ROM BTFSS STATUS,Z CALL DOERROR MOVF RegB,W ;get low byte of address GOTO STOOPX ;store RegA into this address and return ;------------------------------------------------------------------------------- ;$20 ;Form NOS+TOS*2 and then use that value as an address of a word to push onto TOS ; PUSH(NOS+TOS*2). Single-byte instruction. ; DBXOP CALL PULLA ;get TOS into RegA ADDWF RegA ;RegA:= RegA * 2 RLF RegA+1 CALL PBDADD ;get NOS into RegB and RegA:= RegA + RegB CALL FETCHA ;fetch low byte pointed to by RegA CALL PUSH ;push it CALL FETCHA ;fetch high byte GOTO OPGOPW ;go push it ;------------------------------------------------------------------------------- ;$21 ;Load the (logical) address of a variable onto the stack. Conventional three- ; byte instruction: opcode, level, offset. ; ADROP CALL HEAPADR ;fetch level & offset and point W to heap addr GOTO LDXPA ;go push W & a cleared high byte indicating a ; RAM address cuz all heap variables are in RAM ;=============================================================================== ; MISCELLANEOUS OPERATIONS ;=============================================================================== ;$23 ;Short relative jump instruction. BRA 0 branches back to the BRA opcode forming ; an infinite loop. Two-byte instruction: opcode, number of bytes to branch back ; BRAOP CALL FETCH ;get number of opcode bytes to branch back SUBWF I2LPC ;subtract from current I2LPC BTFSS STATUS,C ;skip if no borrow DECF I2LPC+1 MOVLW 2 ;adjust for the two FETCHes that incremented SUBWF I2LPC ; I2LPC twice (once for opcode and once for BTFSS STATUS,C ; the number of bytes to branch back) DECF I2LPC+1 GOTO OPGO ;------------------------------------------------------------------------------- ;$40..$7F ;Short, short immediate load of an 8-bit, signed constant. ; Single-byte instruction. $40 => -1, $41 => 0, $42 => 1, ... $7F => 62. ; SSIMOP MOVLW 41h ;convert opcode to constant by subtracting 41h SUBWF RegX,W GOTO SIMOPX ;enter common code ;------------------------------------------------------------------------------- ;$24 ;TOS:= 8-bit, signed, immediate constant. Two-byte instruction: opcode, constant ; SIMOP CALL FETCH ;get constant byte from opcode SIMOPX MOVWF RegA SIMOPY CLRF RegA+1 ;assume high byte is clear BTFSC RegA,7 ;skip if low byte is positive COMF RegA+1 ; otherwise set high byte to 0FFh (extend sign) GOTO OPGOPA ;go push RegA ;------------------------------------------------------------------------------- ;$25 ;This routine optimizes the case statement a little. It pops TOS, compares it ; to NOS, and takes the jump only if they are not equal. Three-byte instruction: ; opcode, low byte of jump address, high byte of jump address. ; CJPOP CALL PULLB ;TOS into RegB CALL PULLA ;NOS into RegA (low byte of RegA is in W) CALL REPUSH ;effectively push NOS back onto stack CALL REPUSH SUBWF RegB,W ;compare low bytes of NOS to TOS BTFSS STATUS,Z ;skip if they are equal GOTO JMPOP ; otherwise branch MOVF RegA+1,W ;compare high bytes SUBWF RegB+1,W BTFSS STATUS,Z ;skip if equal GOTO JMPOP ; otherwise branch GOTO JPCOPX ;TOS = NOS: move I2LPC past address to jump to ;------------------------------------------------------------------------------- ;$0C ;Routine to call an intrinsic. Note that intrinsics return by a direct jump to ; OPGO. Arguments, if any, are on the stack in the order they are called (TOS ; is last). If an intrinsic returns a value, it will be in TOS. The intrinsic ; must keep the stack balanced. A common way to bomb yourself is to pass the ; wrong number of arguments. Two-byte instruction: opcode, intrinsic number. ; ORG 1FFh ;(RETP for FETCH sets page bits for Jump Table) CMLOP CALL FETCH ;get intrinsic number ADDWF PC ;jump to corresponding routine ;Intrinsic Routine Jump Table: No. / Description GOTO ABS ; 0 Absolute value GOTO RAN ; 1 Random number GOTO REM ; 2 Remainder of last divide GOTO RESERVE ; 3 Reserve array space GOTO SWAPB ; 4 Swap bytes GOTO EXTEND ; 5 Extend sign from low byte GOTO RESTART ; 6 Restart XPL0 program GOTO CHIN ; 7 Input a byte GOTO CHOUT ; 8 Output a byte GOTO CRLF ; 9 New line GOTO INTIN ;10 Input an integer GOTO INTOUT ;11 Output an integer GOTO TEXT ;12 Output a string GOTO OPENI ;13 Initialize input device GOTO OPENO ;14 Initialize output device GOTO CLOSE ;15 Close an output device GOTO RESETX ;16 Reset GOTO TRAP ;17 Set trap flags GOTO FREE ;18 Determine remaining heap space GOTO RERUN ;19 Test rerun flag GOTO POUT ;20 Port output GOTO SETHP ;21 Set heap pointer GOTO GETERR ;22 Get I2L error number GOTO PIN ;23 Port input GOTO SOUND ;24 Squeak the speaker GOTO SETRUN ;25 Set the rerun flag GOTO HEXIN ;26 Input a hex integer GOTO HEXOUT ;27 Output a hex integer GOTO DOCLRWDT ;28 CLRWDT instruction GOTO DOOPTION ;29 OPTION instruction GOTO DOSLEEP ;30 SLEEP instruction ;------------------------------------------------------------------------------- ;GOTO and CALL extenders ; ABSAX FGOTO ABSA PULLAX FGOTO PULLA PULLBX FGOTO PULLB PUSHX FGOTO PUSH ;=============================================================================== ; SUBROUTINES ;=============================================================================== ; ;Pull TOS into NOWDEV. Currently any device number other than 0 is illegal. ; If illegal device number then RegA, RegB, RegC, RegX and FLAGS are changed. ; PULLNOWDEV CALL PULLBX ;pull device number MOVWF NOWDEV ;store low byte into NOWDEV (ignore high byte) BTFSC STATUS,Z ;skip if not device 0 RETP ; else return with no error MOVLW 3 ;flag illegal device number GOTO DOERRORX ;report error and possibly return ;------------------------------------------------------------------------------- ;Output a carriage return and line feed (new line) to NOWDEV. ; DOCRLF MOVLW CR ;carriage return CALL OUTTO MOVLW LF ;line feed GOTO OUTTO ;output byte and return ;------------------------------------------------------------------------------- ;Output a text string pointed to by RegA. The string terminates on a character ; with its MSB (bit 7) set. RegA is left pointing to the end of the string +1. ; Note that the entry point is at TEXTOUT. ; TXT10 CALL OUTTO ;output char TEXTOUT CALL FETCHAX ;get character MOVWF TEMP ;test MSB BTFSS TEMP,7 ;skip if MSB is set GOTO TXT10 ; else loop back ANDLW 7Fh ;clear MSB GOTO OUTTO ;output last char and return ;------------------------------------------------------------------------------- ;Multiply RegA by 16, 4, or 2. The W register is not changed. ; REGAX16 CALL REGAX4 ;multiply RegA by 16 REGAX4 CALL REGAX2 ;multiply RegA by 4 REGAX2 BCF STATUS,C ;multiply RegA by 2 RLF RegA RLF RegA+1 RETP ;------------------------------------------------------------------------------- ;Move RegA to RegB. ; DMOVAB MOVF RegA,W ;move low byte MOVWF RegB MOVF RegA+1,W ;move high byte MOVWF RegB+1 RETP ;------------------------------------------------------------------------------- ;Routine to fetch a byte pointed to by RegA and then bump RegA. (RegA++) -> W. ; This fetches from both RAM and ROM. RAM ranges from $0000 through $00FF, and ; ROM ranges from $0100 through $FFFF. WARNING: This cannot be used to fetch ; from ROM below $0100; specifically, error messages cannot reside below $0100. ; FETCHAX MOVF RegA+1,W ;load and test high byte of address pointer BTFSC STATUS,Z ;skip if it's a ROM address GOTO FETA20 ; else go fetch from RAM ;Fetch from ROM: BTFSC RegA+1,3 ;skip if fetching below 800h GOTO FETA10 ; else go fetch two nibbles MOVWM ;fetch the byte pointed to by RegA MOVF RegA,W IREAD ;fetch byte into W INCFSZ RegA ;increment pointer RETP ; most of the time it returns from here INCF RegA+1 ;increment high byte BTFSS RegA+1,3 ;skip if 800h--ignore reset vector at 7FFh RETP ; return DECF RegA ;convert 800h back to 7FFh DECF RegA+1 ;When fetching at or above address 7FFh, the location to actually fetch from is: ; = (RegA - 7FFh)*2 + PROGLO ; = (RegA - (800h-1))*2 + PROGLO ; = 2*RegA - 1000h + 2 + PROGLO Since 1000h is over the top, it has no effect ; = 2*RegA + PROGLO + 2 FETA10 RLF RegA,W ;RegB:= 2*RegA MOVWF RegB RLF RegA+1,W CALL FETCOM GOTO INCAX ;exit ;Fetch from RAM: FETA20 MOVF RegA,W ;point FSR to RAM address FCALL LOGPHYS ;convert logical address to physical address MOVF IND,W ;fetch byte from RAM BANKX 0 ;restore access to bank 0 INCAX FGOTO INCA ;increment RegA and return ;------------------------------------------------------------------------------- ;Common code for FETCH and FETCHA. FSR is not changed. ; FETCOM MOVWF RegB+1 BCF RegB,0 ;clear possible carry in MOVLW low (PROGLO+2) ;RegB:= RegB + PROGLO + 2 ADDWF RegB BTFSC STATUS,C INCF RegB+1 MOVLW high (PROGLO+2) ADDWF RegB+1 MOVF RegB+1,W ;fetch from location pointed to by RegB MOVWM MOVF RegB,W IREAD MOVMW ;save high nibble in TEMP MOVWF TEMP MOVF RegB+1,W ;fetch from next location MOVWM INCF RegB,W ;(PROGLO must be even to prevent possible carry) IREAD MOVMW ;get low nibble SWAPF TEMP ;combine it with high nibble IORWF TEMP,W RETP ;and return the resulting byte in W ;------------------------------------------------------------------------------- ;Output the 16-bit, signed integer in RegA in ASCII decimal format. RegA, RegB, ; RegC, RegX and FLAGS are changed. ; #define SUPRLZ FLAGS,1 ;flag: suppress leading zeros INTO MOVLW '-' ;get a minus sign BTFSC RegA+1,7 ;skip if RegA is positive CALL OUTTO ; else output the minus sign CALL ABSAX ;use absolute value of RegA MOVLW 4 ;set up loop counter and index for POWER table MOVWF RegC BSF SUPRLZ ;set flag to suppress leading zeros ;Subtract a power-of-10 from RegA until it is negative. Count the number ; of subtractions in RegX. IO20 CLRF RegX ;init subtraction counter DECF RegC,W ;move current power-of-ten into RegB CALL POWERL ;index into POWER table = loop counter -1 MOVWF RegB DECF RegC,W CALL POWERH MOVWF RegB+1 IO30 FCALL DSUB ;subtract power-of-10 from RegA INCF RegX ;count number of subtractions BTFSS RegA+1,7 ;loop until negative result GOTO IO30 FCALL DADD ;add back one power-of-ten DECFSZ RegX,W ;undo one subtraction and get counter in W ;skip if counter is zero BCF SUPRLZ ; else set flag to output zeros from now on IORLW 30h ;convert binary to an ASCII digit BTFSS SUPRLZ ;skip if leading zeros are being suppressed CALL OUTTO ; else output digit DECFSZ RegC ;loop for powers 10000 down to 10 GOTO IO20 MOVF RegA,W ;the one's digit is left in RegA IORLW 030h ;output it whether it's a zero or not GOTO OUTTO ; and return ;Power-of-Ten Tables ; POWERL ADDWF PC RETLW low 10 ;1 RETLW low 100 ;2 RETLW low 1000 ;3 RETLW low 10000 ;4 POWERH ADDWF PC RETLW high 10 ;1 RETLW high 100 ;2 RETLW high 1000 ;3 RETLW high 10000 ;4 ;------------------------------------------------------------------------------- ;Input a signed integer in decimal ASCII format. The 16-bit binary result is ; returned in RegA. RegB, RegX and FLAGS are changed. ; #define SignFlg FLAGS,2 ;sign flag: set if negative number #define NumFlg FLAGS,3 ;number flag: set when digit is read in GETNO II00 CLRF RegA ;initialize CLRF RegA+1 CLRF FLAGS ;clear SignFlg and NumFlg CALL INPB ;read in an ASCII character MOVWF RegX ;save a copy XORLW EOF ;is it an end-of-file character? BTFSC STATUS,Z ;skip if not GOTO II90 ; branch if so--return with RegA = 0 XORLW EOF^'-' ;is character a minus sign? (undoes XOR EOF too) BTFSS STATUS,Z ;skip if so GOTO II30 ; branch if not BSF SignFlg ;set the sign flag II20 CALL INPB ;read in an ASCII digit MOVWF RegX ;save a copy II30 MOVLW '0' ;compare digit to '0' SUBWF RegX ;save result (0-9) in RegX BTFSS STATUS,C ;skip if it's >= '0' GOTO II80 ; branch if digit < '0' MOVLW 10 ;compare resulting digit to 10 SUBWF RegX,W ;(don't mess up RegX) BTFSC STATUS,C ;skip if it's < 10 GOTO II80 ;branch if it's >= 10 BSF NumFlg ;indicate a digit (0-9) was read in CALL DMOVAB ;RegA:= RegA *10 CALL REGAX4 FCALL DADD CALL REGAX2 MOVF RegX,W ;RegA:= RegA + digit ADDWF RegA BTFSC STATUS,C ;propagate carry if necessary (required) INCF RegA+1 GOTO II20 ;loop until a non-digit character is read in II80 BTFSS NumFlg ;come here when a non-digit character is read in GOTO II00 ;start over if no digits were read in BTFSS SignFlg ;if there was no minus sign then II90 RETP ; just return FGOTO NEGA ; else negate RegA and return ;------------------------------------------------------------------------------- ;Output the binary value in RegA as four ASCII hex digits. RegA is preserved; ; RegX is changed. ; HEX4OUT MOVF RegA+1,W ;output high byte CALL HEX2OUT MOVF RegA,W ;get low byte and fall into HEX2OUT... ;------------------------------------------------------------------------------- ;Output the binary value in the W register as two ASCII hex digits. RegX is ; changed. ; HEX2OUT MOVWF RegX ;save copy SWAPF RegX,W ;output high nibble CALL HEX1OUT MOVF RegX,W ;get saved low nibble and fall into HEX1OUT... ;------------------------------------------------------------------------------- ;Output the binary value in the W register as an ASCII hex digit. ; HEX1OUT ANDLW 00Fh ;get nibble MOVWF TEMP ;save copy MOVLW 10 ;compare it to 10 SUBWF TEMP,W MOVLW 'A'-'0'-10 ;set up for case where it's >= 10 BTFSC STATUS,C ;skip if it's less than 10 ADDWF TEMP ; else add 'A' (-'0') to amount nibble is >= 10 MOVLW '0' ;convert to ASCII ADDWF TEMP,W GOTO OUTTO ;output char and return ;------------------------------------------------------------------------------- ;Randomize the random number generator. ; WARNING: A lockup condition exists if all bits in SEED are ones. ; RANDIZE BANKA SEED MOVF RB,W ;RB is not zeroed by initialization code ANDLW 0F7h MOVWF SEED+1 MOVWF SEED+2 BANKX 0 RETP ;=============================================================================== ; I/O ROUTINES ;=============================================================================== ; ;Since there is only one I/O device, the dispatch routine is eliminated. ; BEWARE: These I/O routines must not change any registers used by the ; interpreter (except W and FSR). ; ;------------------------------------------------------------------------------- ;Input an ASCII character and return it in the W register ; INPB RETP ;***INPUTX ;GOTO Rcv *** DEBUG *** ;fall into OUTTO to echo it... ;------------------------------------------------------------------------------- ;Output ASCII character in the W register ; OUTTO RETP ;***OUTPUTX ;GOTO Xmit *** DEBUG *** ;------------------------------------------------------------------------------- ;Initialize device for input ; INIDEV ; RETP ;------------------------------------------------------------------------------- ;Initialize device for output ; INODEV ; RETP ;------------------------------------------------------------------------------- ;Close output device ; CLODEV RETP ;=============================================================================== ; INTRINSIC ROUTINES ;=============================================================================== ;0 ;Intrinsic to return the absolute value of top-of-stack (TOS). ; VAL:= ABS(VAL); ; ABS CALL PULLAX ;pull TOS into RegA CALL ABSAX ;take absolute value of RegA OPGOPAX FGOTO OPGOPA ;go push RegA and return to OPGO ;------------------------------------------------------------------------------- ;1 ;Intrinsic to generate a random number. The value returned is between 0 and ; TOS-1. ; If TOS = 0 then the seed is initialized for a repeatable sequence. ; If TOS < 0 then the seed is randomized and RAN(-TOS) is returned. ; VAL:= RAN(10); \VAL gets 0 through 9 ; RAN CALL PULLAX ;get the limit, which is in TOS IORWF RegA+1,W ;check for limit = 0 BTFSS STATUS,Z ;skip if zero (W holds 0, which is used below) GOTO RAN10 ; else branch if not zero BANKA SEED CLRF SEED ;initialize for a repeatable sequence CLRF SEED+1 CLRF SEED+2 BANKX 0 PUSHW2X FGOTO PUSHW2 ;return a zero (in W) on the stack RAN10 BTFSC RegA+1,7 ;skip if limit is positive CALL RANDIZE ; else randomize seed CALL ABSAX ;use positive range CALL DMOVAB ;copy limit into RegB ;pseudo-random generator using 24-bit feedback shift register BANKA SEED RLF SEED,W ;XNOR the 2 most significant bits XORLW 0FFh XORWF SEED,W MOVWF TEMP ;and shift result into carry ADDWF TEMP RRF SEED+2 ;rotate the entire 24-bit shift register RRF SEED+1 RRF SEED SWAPF SEED+1,W ;move SEED into RegA (backwards) MOVWF RegA SWAPF SEED,W ;scramble the bits a bit MOVWF RegA+1 BCF RegA+1,7 ;force number positive BANKX 0 FCALL DIV ;RegA:= RegA / RegB GOTO REM10 ;go return remainder as the random number ;------------------------------------------------------------------------------- ;2 ;Get remainder of most recent integer division. The argument is an expression ; whose result is thrown away. This expression can contain a division or just ; be zero to get the result of an earlier division. ; VAL:= REM(17/5); \VAL gets 2 ; VAL:= REM(0); ; REM CALL PULLAX ;discard TOS REM10 MOVF REMAIN+1,W ;copy remainder of latest division into RegA MOVWF RegA+1 MOVF REMAIN,W FGOTO OPGOPAW ;go push W & RegA+1 and return to OPGO ;------------------------------------------------------------------------------- ;3 ;Intrinsic to reserve bytes in the heap and return the base address of the ; reserved space. This is the way arrays are created. Since space is reserved ; in the heap allocation of a procedure, the array will disappear when the ; procedure is exited. ; ARRAY:= RESERVE(5*2); \Reserve a 5x3 integer array ; for I:= 0, 5-1 do ARRAY(I):= RESERVE(3*2); ; RESERVE CALL PULLAX ;get number of bytes to reserve MOVF HP,W ;return the current HP on the stack CALL PUSHX ;push low byte (a 0 high byte is pushed later) MOVF RegA,W ;add number of bytes to reserve to current HP ADDWF HP MOVLW 0FFh ;check for memory overflow (error 2) BTFSC STATUS,C ;if there was a carry into high byte of amount MOVWF RegA+1 ; to reserve then force an error (RegA+1:= 0FFh) MOVF RegA+1 ;test high byte of sum BTFSS STATUS,Z ;skip if it's zero MOVWF HP ; else force an error (HP:= 0FFh) FCALL CHKMEM ;check for memory overflow (HP > I2LSP) MOVLW 0 ;push high byte = 0, since RAM starts at $0000 OPGOPWX FGOTO OPGOPW ;------------------------------------------------------------------------------- ;4 ;Intrinsic to swap the high and low bytes of the value in top-of-stack. ; VAL:= SWAP($1234); \VAL gets $3412 ; SWAPB CALL PULLAX ;TOS into RegA MOVF RegA+1,W ;push new low byte CALL PUSHX MOVF RegA,W ;push new high byte GOTO OPGOPWX ;go push W ;------------------------------------------------------------------------------- ;5 ;Intrinsic to extend the sign of the low byte into the high byte. ; VAL:= EXTEND(VAL); ; EXTEND CALL PULLAX ;TOS into RegA FGOTO SIMOPY ;go do it (W = RegA) ;------------------------------------------------------------------------------- ;6 ;Intrinsic to restart the XPL0 program. ; RESTART; ; RESTART MOVLW 0FFh ;set rerun flag to true MOVWF RERUNF GOTO START ;------------------------------------------------------------------------------- ;7 ;Intrinsic to input a byte and return it on the stack. ; VAL:= CHIN(0); ; CHIN CALL PULLNOWDEV ;pull device number CALL INPB ;input a byte LDXPAX FGOTO LDXPA ;go push W reg then push 0 ;------------------------------------------------------------------------------- ;8 ;Intrinsic to output the byte on the stack. ; CHOUT(0, ^A); ; CHOUT CALL PULLAX ;pull byte and save it in RegA CALL PULLNOWDEV ;pull device number MOVF RegA,W ;get byte CALL OUTTO ;send it OPGOX FGOTO OPGO ;------------------------------------------------------------------------------- ;9 ;Intrinsic to output a carriage return and line feed, i.e. start a new line. ; CRLF(0); ; CRLF CALL PULLNOWDEV ;pull device number CALL DOCRLF ;output CR & LF GOTO OPGOX ;------------------------------------------------------------------------------- ;10 ;Intrinsic to input a signed integer and return its value on the stack. ; VAL:= INTIN(0); ; INTIN CALL PULLNOWDEV ;pull device number CALL GETNO ;input the integer into RegA GOTO OPGOPAX ;go push RegA ;------------------------------------------------------------------------------- ;11 ;Intrinsic to output the value on the stack in signed, decimal ASCII format. ; INTOUT(0, -123); ; INTOUT CALL PULLAX ;pull integer into RegA CALL PULLNOWDEV ;pull device number CALL INTO ;output it GOTO OPGOX ;------------------------------------------------------------------------------- ;12 ;Intrinsic to output a text string. ; TEXT(0, "Hello"); ; TEXT CALL PULLAX ;pull address of string into RegA CALL PULLNOWDEV ;pull device number CALL TEXTOUT ;output the string GOTO OPGOX ;------------------------------------------------------------------------------- ;13 ;Intrinsic to open, or initialize, an input device. ; OPENI(0); ; OPENI CALL PULLNOWDEV ;pull device number CALL INIDEV GOTO OPGOX ;------------------------------------------------------------------------------- ;14 ;Intrinsic to open, or initialize, an output device. ; OPENO(0); ; OPENO CALL PULLNOWDEV ;pull device number CALL INODEV GOTO OPGOX ;------------------------------------------------------------------------------- ;15 ;Intrinsic to close an output device. ; CLOSE(0); ; CLOSE CALL PULLNOWDEV ;pull device number CALL CLODEV GOTO OPGOX ;------------------------------------------------------------------------------- ;16 ;Intrinsic to abort the XPL0 program by jumping to the RESET start-up code. ; RESET; ; (No code necessary--see Intrinsic Routine Jump Table.) ; ;------------------------------------------------------------------------------- ;17 ;Intrinsic to set the error trap flags. ; TRAP($FFFD); \Ignore divide by zero (bit 1 is clear) ; TRAP CALL PULLAX ;pull flag bits into RegA MOVWF TRAPS ;copy RegA into TRAPS MOVF RegA+1,W MOVWF TRAPS+1 GOTO OPGOX ;------------------------------------------------------------------------------- ;18 ;Intrinsic to return the number of bytes of unused space available in the heap. ; This space should not all be reserved because some will probably be needed ; for the stack and for local variables in any procedures that are called. ; RESERVE(FREE-8); ; Return logical(I2LSP) - HP ; FREE MOVF I2LSP,W ;convert physical address to logical address ;*** DEBUG ; ANDLW 0Fh ;convert I2LSP to logical address in TEMP ; MOVWF TEMP ;simply shift high nibble of I2LSP right ; RRF I2LSP,W ; one bit, leave low nibble intact ; ANDLW 70h ; IORWF TEMP ; ; MOVF HP,W ;temp - HP ; SUBWF TEMP,W ;return result on stack ; GOTO LDXPAX ;push W reg then push 0 ;------------------------------------------------------------------------------- ;19 ;Intrinsic to return the value of the rerun flag. ; FLAG:= RERUN; ; RERUN MOVF RERUNF,W ;get the flag GOTO PUSHW2X ;go push W twice ;------------------------------------------------------------------------------- ;20 ;Intrinsic to output a byte to any "port" address. "Port" is not restricted ; to locations 5 through 7, thus any RAM location can be written. ; POUT(value, port, mode); ; If "mode" is not 0 then output "value" to the control register specified by ; mode. In this case only these "ports" are valid: ; 5 TRIS RA ; 6 TRIS RB ; 7 TRIS RC ; POUT CALL PULLAX ;pull mode BTFSS STATUS,Z ;skip if mode = 0 GOTO POUT00 ; else go do TRIS CALL PULLBX ;pull port address and save it in RegB CALL PULLAX ;pull byte to output and save it in RegA MOVF RegB,W ;set FSR to port address MOVWF FSR ;BANK 0 IS NO LONGER SELECTED MOVF RegA,W ;get byte to output MOVWF IND ;write it to specified port BANKX 0 ;restore access to bank 0 GOTO OPGOX POUT00 MOVWM ;store pulled mode value into MODE register CALL PULLBX ;pull port address and save it in RegB CALL PULLAX ;pull byte to output, it's in W BTFSC RegB,1 ;port address bits: X01 X10 X11 GOTO POUT20 ;corresponds to: RA RB RC BTFSC RegB,0 TRIS RA GOTO OPGOX POUT20 BTFSS RegB,0 TRIS RB BTFSC RegB,0 TRIS RC GOTO OPGOX ;------------------------------------------------------------------------------- ;21 ;Intrinsic to set the heap pointer. The current value of the heap pointer is ; gotten by calling RESERVE(0). The user should have a good idea of the ; functioning of I2L before dinging with the heap pointer, or he will surely ; bomb himself. ; SETHP($40); ; SETHP CALL PULLAX ;get (logical) address MOVWF HP ;set new heap pointer GOTO OPGOX ;------------------------------------------------------------------------------- ;22 ;Intrinsic to return the latest I2L error number and then clear it. ; ERR:= GETERR; ; GETERR MOVF ERRNO,W ;get error number CLRF ERRNO ;clear error number GOTO LDXPAX ;go push W then push 0 ;------------------------------------------------------------------------------- ;23 ;Intrinsic to read a byte from any "port" address and return it on the stack. ; Port is not restricted to locations 5-7, thus any RAM location can be read. ; variable:= PIN(port, mode); ; PIN CALL PULLAX ;pull mode BTFSS STATUS,Z ;skip if mode = 0 GOTO PIN00 ; else go do TRIS CALL PULLAX ;pull port address MOVWF FSR ;put low byte into FSR MOVF IND,W BANKX 0 ;restore access to bank 0 GOTO LDXPAX ;go push W reg then push 0 PIN00 MOVWM ;store pulled mode value into MODE register CALL PULLAX ;pull port address and discard it TRIS RB ;port is assumed to be RB; swap W with ctrl reg MOVWF RegA ;save control register value in RegA TRIS RB ;swap back to restore original value in ctrl reg CLRF RegA+1 ;clear high byte GOTO OPGOPAX ;go push RegA and return ;------------------------------------------------------------------------------- ;24 ;Intrinsic to emit a sound. ; SOUND(vol, cycles, period) ;The actual period of the square wave depends on the microcontroller oscillator. ; "cycles" is actually "half-cycles". "Vol" (volume) is either full on or off. ; When the volume is off, this intrinsic provides a time delay. ; #define VOL FLAGS,0 ;flag indicating that volume is on SOUND CALL PULLAX ;pull period FCALL PULLC ;pull number of half-cycles CALL PULLBX ;pull volume (on/off) BSF VOL ;assume volume is on IORWF RegB+1 ;if any bit is set, volume is on BTFSC STATUS,Z ;skip if not zero BCF VOL ; else clear volume flag ;Put out RegC half-cycles of sound INCF RegC ;compensate for DECFSZ below INCF RegC+1 ; (RegC might be 0) GOTO SND30 ;go check for zero cycles SND20 MOVLW 80h ;set bit corresponding to speaker BTFSC VOL ;skip if volume is off XORWF RB ; else flip speaker bit CALL DMOVAB ;delay for half a cycle; period -> RegB INCF RegB ;compensate for DECF below INCF RegB+1 SND50 CLRWDT ;kill 5 cycles per loop (in turbo mode) ; (Was an NOP R.O.) DECFSZ RegB ;loop on low byte GOTO SND50 DECFSZ RegB+1 ;loop on high byte GOTO SND50 SND30 DECFSZ RegC ;loop on low cycle byte GOTO SND20 DECFSZ RegC+1 ;loop on high cycle byte GOTO SND20 GOTO OPGOX ;return when cycle count is zero ;------------------------------------------------------------------------------- ;25 ;Intrinsic to set or clear the rerun flag. ; SETRUN(true); ; SETRUN CALL PULLAX ;get TOS IORWF RegA+1,W ;if any bit is set, the flag is set (true) MOVWF RERUNF GOTO OPGOX ;------------------------------------------------------------------------------- ;26 ;Intrinsic to input a hex integer and return it in top-of-stack. ; HEX:= HEXIN(0); ;Input an unsigned, 16-bit ASCII hex number into RegA. Any leading non-hex ; characters are ignored (including a minus sign). The number is terminated ; either by a non-hex character or after 4 digits have been read in. ; RegA and RegX are changed. ; HEXIN CALL PULLNOWDEV ;pull device number CLRF RegA ;initialize hex value CLRF RegA+1 MOVLW 4 ;init digit counter MOVWF RegX HI00 CALL INPB ;read in an ASCII character MOVWF TEMP ;save copy XORLW EOF ;is it an end-of-file character? BTFSC STATUS,Z ;skip if not GOTO HI90 ; branch if it is--return with RegA=0 MOVLW '0' ;subtract lower limit SUBWF TEMP MOVLW 10 ;compare to upper limit (>= 10) SUBWF TEMP BTFSS STATUS,C ;skip if character is > '9' or < '0' GOTO HI30 ; else character is in range '0' through '9' BCF TEMP,5 ;make sure possible 'a'-'f' is uppercase MOVLW 'A'-('0'+10) ;compensate TEMP for above subtracts and SUBWF TEMP ; also subtract 'A' MOVLW 'F'-'A'+1 ;(= 6) test for upper limit of 'F' SUBWF TEMP,W BTFSC STATUS,C ;skip if result is negative--i.e. in range GOTO HI40 ; else not a valid hex digit MOVLW 10 ;get fix-up value HI30 ADDWF TEMP,W ;add 10 to get binary value CALL REGAX16 ;multiply current value by 16 (W is unchanged) IORWF RegA ;insert hex digit DECFSZ RegX ;loop for a maximum of 4 digits GOTO HI00 HI40 BTFSC RegX,2 ;skip if any digits read in GOTO HI00 ; else go back and keep trying HI90 GOTO OPGOPAX ;go push RegA ;------------------------------------------------------------------------------- ;27 ;Intrinsic to output the value in top-of-stack in ASCII hex format. ; HEXOUT(0, $1234); ; HEXOUT CALL PULLAX ;pull integer into RegA CALL PULLNOWDEV ;pull device number CALL HEX4OUT ;output it GOTO OPGOX ;------------------------------------------------------------------------------- ;28 ;Intrinsic to execute CLRWDT instruction. ; CLRWDT; ; DOCLRWDT CLRWDT ;clear WDT & prescaler; set STATUS,TO & PD GOTO OPGOX ;------------------------------------------------------------------------------- ;29 ;Intrinsic to set the OPTION register. ; OPTION($85); \enable RTCC interrupt and set prescaler to divide by 64 ; DOOPTION CALL PULLAX ;pull integer into RegA, W = low byte OPTION ;move W to OPTION register GOTO OPGOX ;------------------------------------------------------------------------------- ;30 ;Intrinsic to execute SLEEP instruction. ; SLEEP; ; DOSLEEP SLEEP ;clear WDT & prescaler; set STATUS,TO & clear PD GOTO OPGOX ; *** DEBUG *** ;------------------------------------------------------------------------------- ;I2L error handler. Call with error number in W register. Possible errors are: ; 0: RETURN FROM MAIN ; 1: DIV BY 0 ; 2: OUT OF MEMORY ; 3: I/O ERROR (ILLEGAL DEVICE NUMBER) ; 4: BAD OPCODE (DISABLED) ; 5: BAD INTRINSIC (DISABLED) ; 15: STORE INTO ROM ; If the corresponding bit in the TRAP flags is clear then this routine returns, ; otherwise it is a fatal error and the interpreter is restarted, which restarts ; the XPL0 program. If this returns, ERRNO, RegC and RegX are changed. ; DOERRORX MOVWF ERRNO ;save the error number MOVWF RegX ;set up loop counter MOVF TRAPS,W ;use copy of trap flags MOVWF RegC MOVF TRAPS+1,W MOVWF RegC+1 ERR10 RRF RegC+1 ;shift bit corresponding to error into bit 0 RRF RegC DECFSZ RegX GOTO ERR10 ;loop BTFSS RegC,0 ;if this trap bit is clear then return and RETP ; ignore the error, else fall into ERREXIT... ;------------------------------------------------------------------------------- ;Send an error message and restart the interpreter ; ERREXIT CLRF NOWDEV ;send I2L error message to console CALL DOCRLF ;new line MOVLW low ERRMSG ;display: "Error " MOVWF RegA MOVLW high ERRMSG MOVWF RegA+1 CALL TEXTOUT MOVF ERRNO,W ;display error number (can be 0) MOVWF RegA CLRF RegA+1 CALL INTO CALL DOCRLF ;new line GOTO START ;restart interpreter ;ERRMSG DT Bel, "Error", Sp+80h ERRMSG DT Bel ;(for SxSim) *** DEBUG *** DT 'E' DT 'r' DT 'r' DT 'o' DT 'r' DT ' '+80h ;WARNING: Messages in ROM cannot reside below 100h because of how FETCHA works. ;=============================================================================== ; RESET ENTRY POINT ;=============================================================================== RESETX BTFSS STATUS,TO ;If TO=0 then WDT timeout occurred GOTO START ; bypass clearing RAM and do a restart ;Clear RAM from 08h up through highest enabled bank. Also clears FSR. CLRF FSR RES10 BTFSS FSR,4 ;skip if 10-1F in each bank BSF FSR,3 ; else skip if 0-7 (skip special registers) CLRF IND ;clear location INCFSZ FSR GOTO RES10 ;Reset clears rerun flag (RERUNF). Restart leaves it set. START MOVLW STACK ;initialize interpreter's stack pointer MOVWF I2LSP MOVLW HEAPLO ;initialize heap pointer to base of heap space MOVWF HP MOVWF DISPLY ;also init level 0 in display vector table CLRF LEVEL MOVLW 0FFh ;trap all errors MOVWF TRAPS MOVWF TRAPS+1 CLRF ERRNO ;clear error number ;Initialize intrinsic routines CALL RANDIZE ;randomize random number generator MOVLW low PROGLO ;set interpreter's program counter to start MOVWF I2LPC ; of I2L code MOVLW high PROGLO MOVWF I2LPC+1 GOTO OPGOX ;go start interpreting ;=============================================================================== ;16-bit, unsigned divide. RegA:= RegA / RegB. Remainder in REMAIN. ; ; REMAIN <-- RegA RegX ; - RegB ; ORG 400h DIV CLRF REMAIN ;initialize remainder "register" CLRF REMAIN+1 MOVLW 17 ;initialize loop counter MOVWF RegX GOTO DIV20 ;(carry doesn't matter cuz RegA is shifted 17x) DIV10 RLF REMAIN ;shift in high bit from RegA RLF REMAIN+1 MOVF RegB+1,W ;compare REMAIN to RegB SUBWF REMAIN+1,W ;compare high bytes BTFSS STATUS,Z ;skip if equal GOTO DIV15 ; else branch if not equal MOVF RegB,W ;compare low bytes SUBWF REMAIN,W DIV15 BTFSS STATUS,C ;skip if REMAIN >= RegB (carry is set) GOTO DIV20 ; otherwise branch (carry is clear) MOVF RegB,W ;REMAIN:= REMAIN - RegB SUBWF REMAIN ;subtract low bytes MOVF RegB+1,W ;get ready to subtract high bytes BTFSS STATUS,C ;skip if there was no borrow from high byte INCFSZ RegB+1,W ; else increase amount to subtract by 1; if it's SUBWF REMAIN+1 ; 0 then high byte doesn't change, carry is set DIV20 RLF RegA ;shift carry bit into quotient RLF RegA+1 DECFSZ RegX ;loop until done (don't disturb carry) GOTO DIV10 RETP ;=============================================================================== ; INTERRUPT SERVICE ROUTINE ;=============================================================================== ; ISRX MOVLW -100 ;interrupt every 100 RTCC cycles RETIW ;NOTE: If code is added, PROGLO will move, and RUN.CMD might need to be changed. ;=============================================================================== ; I2L CODE ;=============================================================================== ERRORLEVEL -306 ;don't display "crossing page boundary" message ORG ($+1)&0FFEh ;this must agree with loc used by SXLODI2L.XPL ; and it must be even because of FETCOM ;------------------------------------------------------------------------------- ;Example showing how an XPL0 program is compiled into .I2L code and how the ; loader converts it to DATA instructions. ; ;XPL0 program: ; loop Text(0, "Hello World! "); ; ;I2L code (with commentary added): ; ;0000 0905 HPI 5 reserve space for global 0 (a real) ; 41 IMM 0 push device 0 ; 26*0000 JSR push address of string and jump over it ; ;0006 48656C6C6F20576F726C642120 "Hello World! " ; ;0012 A0 terminator (space char with MSB set) ; ;0013 ; ^0004 fix JSR address to jump here ; 0C0C CML Text call intrinsic routine to output string ; 2313 BRA loop branch back ; $ end-of-file marker ; ;I2L code converted to (unpacked) DATA instructions by SXLODI2L: ; ;PROGLO EQU $ ; DATA 09h, 05h ; DATA 41h ; DATA 26h ; DATA 13h+low PROGLO, 00h+high PROGLO ; DATA 'H' ; DATA 'e' ; DATA 'l' ; DATA 'l' ; DATA 'o' ; DATA ' ' ; DATA 'W' ; DATA 'o' ; DATA 'r' ; DATA 'l' ; DATA 'd' ; DATA '!' ; DATA ' '|80h ; DATA 0Ch, 0Ch ; DATA 23h, 13h ; ; ORG 7FFh ; GOTO RESET ; END ;-------------------------------------------------------------------------------
file: /Techref/scenix/xpl0/I2L.ASM, 76KB, , updated: 2000/5/12 17:20, local time: 2024/12/10 00:25,
18.97.14.83:LOG IN
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