AS65 Assembler for R6502 [1.42]. Copyright 1994-2007, Frank A. Kingswood Page 1 ----------------------------------------------------- 6502_decimal_test.a65 ------------------------------------------------------ 355 lines read, no errors in pass 1. ; Verify decimal mode behavior ; Written by Bruce Clark. This code is public domain. ; see http://www.6502.org/tutorials/decimal_mode.html ; ; Returns: ; ERROR = 0 if the test passed ; ERROR = 1 if the test failed ; modify the code at the DONE label for desired program end ; ; This routine requires 17 bytes of RAM -- 1 byte each for: ; AR, CF, DA, DNVZC, ERROR, HA, HNVZC, N1, N1H, N1L, N2, N2L, NF, VF, and ZF ; and 2 bytes for N2H ; ; Variables: ; N1 and N2 are the two numbers to be added or subtracted ; N1H, N1L, N2H, and N2L are the upper 4 bits and lower 4 bits of N1 and N2 ; DA and DNVZC are the actual accumulator and flag results in decimal mode ; HA and HNVZC are the accumulator and flag results when N1 and N2 are ; added or subtracted using binary arithmetic ; AR, NF, VF, ZF, and CF are the predicted decimal mode accumulator and ; flag results, calculated using binary arithmetic ; ; This program takes approximately 1 minute at 1 MHz (a few seconds more on ; a 65C02 than a 6502 or 65816) ; ; Configuration: 0001 = cputype = 1 ; 0 = 6502, 1 = 65C02, 2 = 65C816 0000 = vld_bcd = 0 ; 0 = allow invalid bcd, 1 = valid bcd only 0000 = chk_a = 0 ; check accumulator 0000 = chk_n = 0 ; check sign (negative) flag 0000 = chk_v = 0 ; check overflow flag 0000 = chk_z = 0 ; check zero flag 0001 = chk_c = 1 ; check carry flag end_of_test macro db $db ;execute 65C02 stop instruction endm bss 0000 = org 0 ; operands - register Y = carry in 0000 = N1 ds 1 0001 = N2 ds 1 ; binary result 0002 = HA ds 1 0003 = HNVZC ds 1 ;04 ; decimal result 0004 = DA ds 1 0005 = DNVZC ds 1 ; predicted results 0006 = AR ds 1 0007 = NF ds 1 ;08 0008 = VF ds 1 0009 = ZF ds 1 000a = CF ds 1 000b = ERROR ds 1 ;0C ; workspace 000c = N1L ds 1 000d = N1H ds 1 000e = N2L ds 1 000f = N2H ds 2 code 0200 = org $200 0200 : a001 TEST ldy #1 ; initialize Y (used to loop through carry flag values) 0202 : 840b sty ERROR ; store 1 in ERROR until the test passes 0204 : a900 lda #0 ; initialize N1 and N2 0206 : 8500 sta N1 0208 : 8501 sta N2 020a : a501 LOOP1 lda N2 ; N2L = N2 & $0F 020c : 290f and #$0F ; [1] see text if vld_bcd = 1 cmp #$0a bcs NEXT2 endif 020e : 850e sta N2L 0210 : a501 lda N2 ; N2H = N2 & $F0 0212 : 29f0 and #$F0 ; [2] see text if vld_bcd = 1 cmp #$a0 bcs NEXT2 endif 0214 : 850f sta N2H 0216 : 090f ora #$0F ; N2H+1 = (N2 & $F0) + $0F 0218 : 8510 sta N2H+1 021a : a500 LOOP2 lda N1 ; N1L = N1 & $0F 021c : 290f and #$0F ; [3] see text if vld_bcd = 1 cmp #$0a bcs NEXT1 endif 021e : 850c sta N1L 0220 : a500 lda N1 ; N1H = N1 & $F0 0222 : 29f0 and #$F0 ; [4] see text if vld_bcd = 1 cmp #$a0 bcs NEXT1 endif 0224 : 850d sta N1H 0226 : 204102 jsr ADD 0229 : 20c602 jsr A6502 022c : 20bf02 jsr COMPARE 022f : d00f bne DONE ; jsr SUB ; jsr S6502 ; jsr COMPARE ; bne DONE 0231 : e600 NEXT1 inc N1 ; [5] see text 0233 : d0e5 bne LOOP2 ; loop through all 256 values of N1 0235 : e601 NEXT2 inc N2 ; [6] see text 0237 : d0d1 bne LOOP1 ; loop through all 256 values of N2 0239 : 88 dey 023a : 10ce bpl LOOP1 ; loop through both values of the carry flag 023c : a900 lda #0 ; test passed, so store 0 in ERROR 023e : 850b sta ERROR 0240 : DONE end_of_test 0240 : db > db $db ;execute 65C02 stop instruction ; Calculate the actual decimal mode accumulator and flags, the accumulator ; and flag results when N1 is added to N2 using binary arithmetic, the ; predicted accumulator result, the predicted carry flag, and the predicted ; V flag ; 0241 : f8 ADD sed ; decimal mode 0242 : c001 cpy #1 ; set carry if Y = 1, clear carry if Y = 0 0244 : a500 lda N1 0246 : 6501 adc N2 0248 : 8504 sta DA ; actual accumulator result in decimal mode 024a : 08 php 024b : 68 pla 024c : 8505 sta DNVZC ; actual flags result in decimal mode 024e : d8 cld ; binary mode 024f : c001 cpy #1 ; set carry if Y = 1, clear carry if Y = 0 0251 : a500 lda N1 0253 : 6501 adc N2 0255 : 8502 sta HA ; accumulator result of N1+N2 using binary arithmetic 0257 : 08 php 0258 : 68 pla 0259 : 8503 sta HNVZC ; flags result of N1+N2 using binary arithmetic 025b : c001 cpy #1 025d : a50c lda N1L 025f : 650e adc N2L 0261 : c90a cmp #$0A 0263 : a200 ldx #0 0265 : 9006 bcc A1 0267 : e8 inx 0268 : 6905 adc #5 ; add 6 (carry is set) 026a : 290f and #$0F 026c : 38 sec 026d : 050d A1 ora N1H ; ; if N1L + N2L < $0A, then add N2 & $F0 ; if N1L + N2L >= $0A, then add (N2 & $F0) + $0F + 1 (carry is set) ; 026f : 750f adc N2H,x 0271 : 08 php 0272 : b004 bcs A2 0274 : c9a0 cmp #$A0 0276 : 9003 bcc A3 0278 : 695f A2 adc #$5F ; add $60 (carry is set) 027a : 38 sec 027b : 8506 A3 sta AR ; predicted accumulator result 027d : 08 php 027e : 68 pla 027f : 850a sta CF ; predicted carry result 0281 : 68 pla ; ; note that all 8 bits of the P register are stored in VF ; 0282 : 8508 sta VF ; predicted V flags 0284 : 60 rts ; Calculate the actual decimal mode accumulator and flags, and the ; accumulator and flag results when N2 is subtracted from N1 using binary ; arithmetic ; 0285 : f8 SUB sed ; decimal mode 0286 : c001 cpy #1 ; set carry if Y = 1, clear carry if Y = 0 0288 : a500 lda N1 028a : e501 sbc N2 028c : 8504 sta DA ; actual accumulator result in decimal mode 028e : 08 php 028f : 68 pla 0290 : 8505 sta DNVZC ; actual flags result in decimal mode 0292 : d8 cld ; binary mode 0293 : c001 cpy #1 ; set carry if Y = 1, clear carry if Y = 0 0295 : a500 lda N1 0297 : e501 sbc N2 0299 : 8502 sta HA ; accumulator result of N1-N2 using binary arithmetic 029b : 08 php 029c : 68 pla 029d : 8503 sta HNVZC ; flags result of N1-N2 using binary arithmetic 029f : 60 rts if cputype != 1 ; Calculate the predicted SBC accumulator result for the 6502 and 65816 ; SUB1 cpy #1 ; set carry if Y = 1, clear carry if Y = 0 lda N1L sbc N2L ldx #0 bcs S11 inx sbc #5 ; subtract 6 (carry is clear) and #$0F clc S11 ora N1H ; ; if N1L - N2L >= 0, then subtract N2 & $F0 ; if N1L - N2L < 0, then subtract (N2 & $F0) + $0F + 1 (carry is clear) ; sbc N2H,x bcs S12 sbc #$5F ; subtract $60 (carry is clear) S12 sta AR rts endif if cputype = 1 ; Calculate the predicted SBC accumulator result for the 6502 and 65C02 ; 02a0 : c001 SUB2 cpy #1 ; set carry if Y = 1, clear carry if Y = 0 02a2 : a50c lda N1L 02a4 : e50e sbc N2L 02a6 : a200 ldx #0 02a8 : b004 bcs S21 02aa : e8 inx 02ab : 290f and #$0F 02ad : 18 clc 02ae : 050d S21 ora N1H ; ; if N1L - N2L >= 0, then subtract N2 & $F0 ; if N1L - N2L < 0, then subtract (N2 & $F0) + $0F + 1 (carry is clear) ; 02b0 : f50f sbc N2H,x 02b2 : b002 bcs S22 02b4 : e95f sbc #$5F ; subtract $60 (carry is clear) 02b6 : e000 S22 cpx #0 02b8 : f002 beq S23 02ba : e906 sbc #6 02bc : 8506 S23 sta AR ; predicted accumulator result 02be : 60 rts endif ; Compare accumulator actual results to predicted results ; ; Return: ; Z flag = 1 (BEQ branch) if same ; Z flag = 0 (BNE branch) if different ; 02bf : COMPARE if chk_a = 1 lda DA cmp AR bne C1 endif if chk_n = 1 lda DNVZC ; [7] see text eor NF and #$80 ; mask off N flag bne C1 endif if chk_v = 1 lda DNVZC ; [8] see text eor VF and #$40 ; mask off V flag bne C1 ; [9] see text endif if chk_z = 1 lda DNVZC eor ZF ; mask off Z flag and #2 bne C1 ; [10] see text endif if chk_c = 1 02bf : a505 lda DNVZC 02c1 : 450a eor CF 02c3 : 2901 and #1 ; mask off C flag endif 02c5 : 60 C1 rts ; These routines store the predicted values for ADC and SBC for the 6502, ; 65C02, and 65816 in AR, CF, NF, VF, and ZF if cputype = 0 A6502 lda VF ; 6502 ; ; since all 8 bits of the P register were stored in VF, bit 7 of VF contains ; the N flag for NF ; sta NF lda HNVZC sta ZF rts S6502 jsr SUB1 lda HNVZC sta NF sta VF sta ZF sta CF rts endif if cputype = 1 02c6 : a506 A6502 lda AR ; 65C02 02c8 : 08 php 02c9 : 68 pla 02ca : 8507 sta NF 02cc : 8509 sta ZF 02ce : 60 rts 02cf : 20a002 S6502 jsr SUB2 02d2 : a506 lda AR 02d4 : 08 php 02d5 : 68 pla 02d6 : 8507 sta NF 02d8 : 8509 sta ZF 02da : a503 lda HNVZC 02dc : 8508 sta VF 02de : 850a sta CF 02e0 : 60 rts endif if cputype = 2 A6502 lda AR ; 65C816 php pla sta NF sta ZF rts S6502 jsr SUB1 lda AR php pla sta NF sta ZF lda HNVZC sta VF sta CF rts endif 02cf = end TEST No errors in pass 2.