Sweet 16 for Bibo Assembler#
General Information
Author: Steve "Woz" Wozniak
Assembler: BiboAssembler
Published: 1977
see also Original Sweet 16
- The ATARI uses the zero page registers at $E0-$FF instead of $00-$1F
- the "save" and "restore" routines are not in ROM, but in the source
Download: Sweet16Bibo/sweet16.atr
00000 .LI OFF 00010 *************************** 00020 * * 00030 * APPLE II PSEUDO MACHINE * 00040 * INTERPRETER * 00050 * * 00060 * COPYRIGHT (C) 1977 * 00070 * APPLE COMPUTER INC. * 00080 * * 00090 * STEVE WOZNIAK * 00100 * * 00110 *************************** 00120 * TITLE: SWEET 16 INTERPRETER 00130 ; 00140 R0L = $E0 00150 R0H = $E1 00160 R14H = $FD 00170 R15L = $FE 00180 R15H = $FF 00190 ; 00200 .OR $7889 00210 ; .OF D:SWEET16.COM 00220 ; 00230 ; PRESERVE 6502 REG CONTENT 00240 ; 00250 SW16 JSR SAVE 00260 ; 00270 ; INIT SWEET16 PC 00280 ; FROM RETURN ADDRESS 00290 ; 00300 SW16A PLA 00310 STA R15L 00320 PLA 00330 STA R15H 00340 ; 00350 ; INTERPRET AND EXECUTE 00360 ; ONE SWEET16 INSTRUCTION 00370 ; 00380 SW16B JSR SW16C 00390 JMP SW16B 00400 ; 00410 ; INCREMENT SWEET16 PC 00420 ; FOR FETCH 00430 ; 00440 SW16C INC R15L 00450 BNE SW16D 00460 INC R15H 00470 ; 00480 ; COMMON HIG BZTE FOR ALL 00490 ; ROUTINES, PUSH ON STACK FOR 00500 ; RTS 00510 SW16D LDA /SET 00520 PHA 00530 ; 00540 ; FETCH INSTRUCTION 00550 ; 00560 LDY #$0 00570 LDA (R15L),Y 00580 ; 00590 ; MASK REGISTER SPECIFICATION 00600 ; 00610 AND #$F 00620 ; 00630 ; DOUBLE FOR TWO BYTE REGISTERS 00640 ; 00650 ASL 00660 ; 00670 ; TO X REGISTER FOR INDEXING 00680 ; 00690 TAX 00700 LSR 00710 ; 00720 ; NOW HAVE OPCODE 00730 ; 00740 EOR (R15L),Y 00750 ; 00760 ; IF ZERO THEN NO REG OPCODE 00770 ; 00780 BEQ TOBR 00790 ; 00800 ; INDICATE PRIOR RESULT REG 00810 ; 00820 STX R14H 00830 ; 00840 ; OPCODE * 2 TO LSB'S 00850 ; 00860 LSR 00870 LSR 00880 LSR 00890 ; 00900 ; TO Y REGISTER FOR INDEXING 00910 ; 00920 TAY 00930 ; 00940 ; LOW ORDER ADR BYTE ON STACK 00950 ; 00960 LDA OPTBL-2,Y 00970 PHA 00980 ; 00990 ; GOTO REG-OPCODE ROUTINE 01000 ; 01010 RTS 01020 ; 01030 ; INCREMENT PC 01040 ; 01050 TOBR INC R15L 01060 BNE TOBR2 01070 INC R15H 01080 ; 01090 ; LOW ORDER ADR BYTE ONTO 01100 ; STACK FOR NON-REG OPCODE 01110 ; 01120 TOBR2 LDA BRTBL,X 01130 PHA 01140 ; 01150 ; PRIOR RESULT REG INDEX 01160 ; 01170 LDA R14H 01180 ; 01190 ; PREPARE CARRY FOR BC. BNC. 01200 ; 01210 LSR 01220 ; 01230 ; GOTO NON-REG OPCODE ROUTINE 01240 ; 01250 RTS 01260 ; 01270 ; RETURN TO 6502 MODE ROUTINE 01280 ; 01290 ; POP RETURN ADDRESS 01300 ; 01310 RTNZ PLA 01320 PLA 01330 ; 01340 ; RESTORE 6502 REG CONTENT 01350 ; 01360 JSR RESTORE 01370 ; 01380 ; RETURN TO 6502 CODE VIA PC 01390 ; 01400 JMP (R15L) 01410 ; 01420 ; SET REGISTER ROUTINE 01430 ; 01440 ; GET HIGH BYTE OF CONSTANT 01450 ; 01460 SETZ LDA (R15L),Y 01470 STA R0H,X 01480 DEY 01490 ; 01500 ; GET LOW BYTE OF CONSTANT 01510 ; 01520 LDA (R15L),Y 01530 STA R0L,X 01540 ; 01550 ; Y REG CONTAINS 1 01560 ; 01570 TYA 01580 ; 01590 ; ADD 2 TO PC 01600 ; 01610 SEC 01620 ADC R15L 01630 STA R15L 01640 BCC SET2 01650 INC R15H 01660 SET2 RTS 01670 ; 01680 ; OPCODE TABLE 01690 ; 01700 OPTBL .DA #SET-1 ; 1X 01710 BRTBL .DA #RTN-1 ; 0 01720 .DA #LD-1 ; 2X 01730 .DA #BR-1 ; 1 01740 .DA #ST-1 ; 3X 01750 .DA #BNC-1 ; 2 01760 .DA #LDAT-1 ; 4X 01770 .DA #BC-1 ; 3 01780 .DA #STAT-1 ; 5X 01790 .DA #BP-1 ; 4 01800 .DA #LDDAT-1 ; 6X 01810 .DA #BM-1 ; 5 01820 .DA #STDAT-1 ; 7X 01830 .DA #BZ-1 ; 6 01840 .DA #POP-1 ; 8X 01850 .DA #BNZ-1 ; 7 01860 .DA #STPAT-1 ; 9X 01870 .DA #BM1-1 ; 8 01880 .DA #ADD-1 ; AX 01890 .DA #BNM1-1 ; 9 01900 .DA #SUB-1 ; BX 01910 .DA #BK-1 ; A 01920 .DA #POPD-1 ; CX 01930 .DA #RS-1 ; B 01940 .DA #CPR-1 ; DX 01950 .DA #BS-1 ; C 01960 .DA #INR-1 ; EX 01970 .DA #NUL-1 ; D 01980 .DA #DCR-1 ; FX 01990 .DA #NUL-1 ; E 02000 .DA #NUL-1 ; UNUSED 02010 .DA #NUL-1 ; F 02020 ; 02030 ; THE FOLLOWING CODE MUST 02040 ; BE CONTAINED IN A SINGLE PAGE 02050 ; 02060 SET JMP SETZ ; ALWAYS 02070 LD LDA R0L,X 02080 BK = LD+1 02090 STA R0L 02100 ; 02110 ; MOV RX TO R0 02120 ; 02130 LDA R0H,X 02140 STA R0H 02150 RTS 02160 ; 02170 ST LDA R0L 02180 ; 02190 ; MOV R0 TO RX 02200 ; 02210 STA R0L,X 02220 LDA R0H 02230 STA R0H,X 02240 RTS 02250 ; 02260 ; STORE BYTE INDEIRECT 02270 ; 02280 STAT LDA R0L 02290 STAT2 STA (R0L,X) 02300 LDY #$0 02310 ; 02320 ; INDICATE R0 IS RESULT NEG 02330 ; 02340 STAT3 STY R14H 02350 INR INC R0L,X 02360 BNE INR2 ; INC RX 02370 INC R0H,X 02380 INR2 RTS 02390 ; 02400 ; LOAD INDIRECT (RX) TO R0 02410 ; 02420 LDAT LDA (R0L,X) 02430 STA R0L 02440 ; 02450 ; ZERO HIGH ORDER R0 BYTE 02460 ; 02470 LDY #$0 02480 STY R0H 02490 BEQ STAT3 ; ALWAYS 02500 ; 02510 ; HIGH ORDER BYTE = 0 02520 ; 02530 POP LDY #$0 02540 BEQ POP2 ; ALWAYS 02550 POPD JSR DCR ; DECR RX 02560 ; 02570 ; POP HIGH ORDER BYTE @RX 02580 ; AND SAV IN Y REG 02590 ; 02600 LDA (R0L,X) 02610 TAY 02620 POP2 JSR DCR ; DECR RX 02630 ; 02640 ; LOW ORDER BYTE TO R0 02650 ; 02660 LDA (R0L,X) 02670 STA R0L 02680 STY R0H 02690 ; 02700 ; INDICATE R0 AS LAST RES. REG 02710 ; 02720 POP3 LDY #$0 02730 STY R14H 02740 RTS 02750 ; 02760 ; LOW ORDER BYTE TO R0, INC RX 02770 ; 02780 LDDAT JSR LDAT 02790 ; 02800 ; HIGH ORDER BYTE TO R0 02810 LDA (R0L,X) 02820 STA R0H 02830 JMP INR ; INC RX 02840 ; 02850 ; STORE INDIRECT LOW ORDER 02860 ; BYTE AND INC RX THEN 02870 ; STORE HIGH ORDER BYTE, 02880 ; INC RX AND RETURN 02890 ; 02900 STDAT JSR LDAT 02910 LDA R0H 02920 STA (R0L,X) 02930 JMP INR 02940 STPAT JSR DCR ; DEC RX 02950 LDA R0L 02960 ; 02970 ; STORE R0 LOW BYTE @RX 02980 ; 02990 STA (R0L,X) 03000 ; 03010 ; INDICATE R0 AS LAST RES REG 03020 ; 03030 JMP POP3 03040 ; 03050 DCR LDA R0L,X 03060 BNE DCR2 ; DEC RX 03070 DEC R0H,X 03080 DCR2 DEC R0L,X 03090 RTS 03100 ; 03110 ; RESULT TO R0 03120 ; 03130 SUB LDY #$0 03140 ; 03150 ; NOTE Y REG = 13 * 2 FOR CPR 03160 ; 03170 CPR SEC 03180 LDA R0L 03190 SBC R0L,X 03200 STA R0L,Y ; RY=R0-RX 03210 LDA R0H 03220 SBC R0H,X 03230 SUB2 STA R0H,Y 03240 ; 03250 ; LAST RESULT REG * 2 03260 ; 03270 TYA 03280 ; 03290 ; CARRY TO LSB 03300 ; 03310 ADC #$0 03320 STA R14H 03330 RTS 03340 ; 03350 ADD LDA R0L 03360 ADC R0L,X 03370 STA R0L ; R0=RX+R0 03380 LDA R0H 03390 ADC R0H,X 03400 ; 03410 ; R0 FOR RESULT 03420 ; 03430 LDY #$0 03440 ; FINISH ADD 03450 BEQ SUB2 03460 ; 03470 ; NOTE X REG IS 12 * 2 ! 03480 ; 03490 BS LDA R15L 03500 ; 03510 ; PUSH LOW PC BYTE VIA R12 03520 ; 03530 JSR STAT2 03540 LDA R15H 03550 ; 03560 ; PUSH HIGH PC BYTE 03570 ; 03580 JSR STAT2 03590 BR CLC 03600 BNC BCS BNC2 ; NO CARRY TEST 03610 ; 03620 ; DISPLACEMENT BYTE 03630 ; 03640 BR1 LDA (R15L),Y 03650 BPL BR2 03660 DEY 03670 ; 03680 ; ADD TO PC 03690 ; 03700 BR2 ADC R15L 03710 STA R15L 03720 TYA 03730 ADC R15H 03740 STA R15H 03750 BNC2 RTS 03760 BC BCS BR 03770 RTS 03780 ; 03790 ; DOUBLE RESULT REG INDEX 03800 ; 03810 BP ASL 03820 ; 03830 ; TO X REG FOR INDEX 03840 ; 03850 TAX 03860 ; TEST FOR PLUS, BRANCH IF SO 03870 ; 03880 LDA R0H,X 03890 BPL BR1 03900 RTS 03910 ; 03920 ; DOUBLE RESULT REG INDEX 03930 ; 03940 BM ASL 03950 TAX 03960 ; 03970 ; TEST FOR MINUS 03980 ; 03990 LDA R0H,X 04000 BMI BR1 04010 RTS 04020 ; 04030 ; DOUBLE RESULT REG INDEX 04040 ; 04050 BZ ASL 04060 TAX 04070 ; 04080 ; TEST FOR ZERO (BOTH BYTES) 04090 ; 04100 LDA R0L,X 04110 ORA R0H,X 04120 BEQ BR1 04130 RTS 04140 ; 04150 ; DOUBLE RESULT REG INDEX 04160 ; 04170 BNZ ASL 04180 TAX 04190 ; 04200 ; TEST FOR NON-ZERO (BOTH) 04210 ; 04220 LDA R0L,X 04230 ORA R0H,X 04240 BNE BR1 04250 RTS 04260 ; 04270 ; DOUBLE RESULT REG INDEX 04280 ; 04290 BM1 ASL 04300 TAX 04310 ; 04320 ; TEST FOR $FF (-1) BOTH BYTES 04330 ; 04340 LDA R0L,X 04350 AND R0H,X 04360 EOR #$FF 04370 BEQ BR1 04380 RTS 04390 ; 04400 ; DOUBLE RESULT REG 04410 ; 04420 BNM1 ASL 04430 TAX 04440 ; 04450 ; TEST FOR NO $FF 04460 ; 04470 LDA R0L,X 04480 AND R0H,X 04490 EOR #$FF 04500 BNE BR1 04510 NUL RTS 04520 ; 12*2 FOR R12 AS STACK POINTER 04530 ; 04540 RS LDX #$18 04550 ; 04560 ; DECR STACK POINTER 04570 ; 04580 JSR DCR 04590 ; 04600 ; POP HIGHRETURN ADDRESS TO PC 04610 ; 04620 LDA (R0L,X) 04630 STA R15H 04640 ; 04650 ; SAME WITH LOW ORDER BYTE 04660 ; 04670 JSR DCR 04680 LDA (R0L,X) 04690 STA R15L 04700 RTS 04710 RTN JMP RTNZ 04720 ------------------------------ 04730 SAVE 04740 STA ACC 04750 STX XREG 04760 STY YREG 04770 PHP 04780 PLA 04790 STA STATUS 04800 CLD 04810 RTS 04820 ------------------------------ 04830 RESTORE LDA STATUS 04840 PHA 04850 LDA ACC 04860 LDX XREG 04870 LDY YREG 04880 PLP 04890 RTS 04900 ------------------------------ 04910 ACC .HX 00 04920 XREG .HX 00 04930 YREG .HX 00 04940 STATUS .HX 00 04950 ------------------------------ 04960 TEST 04970 JSR SW16 04980 .HX 1100F0 ; SET R1 04990 .HX 120040 ; SET R2 05000 .HX 130002 ; SET R3 05010 .HX 41 ; LD @R1 05020 .HX 52 ; ST @R2 05030 .HX F3 ; DCR R3 05040 .HX 07FB ; BNZ -4 05050 .HX 00 ; RTN 05060 RTS 05070 ------------------------------