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Implement _sbc. They must have many bugs, but anyway, finished.

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This commit is contained in:
Takashi Toyoshima 2014-12-07 12:56:02 +09:00
parent 14fa2b22c3
commit 7370d07645
1 changed files with 55 additions and 1 deletions
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56
6502.S
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@ -532,7 +532,61 @@
.endm
.macro _sbc
// TODO
mov r1, RA
subs r1, r1, r0
movs r2, #FLAG_C
tst SR, r2
beq 1f
subs r1, r1, #1
1:
movs r2, #FLAG_D
tst SR, r2
beq 1f
movs r2, #0x1f
ands r1, r1, r2
mov T0, RA
lsrs T0, T0, #8
mov T1, r0
lsrs T1, T1, #8
subs r2, T0, T1
cmp r1, #10
blo 2f
subs r1, r1, #6
subs r2, r2, #1
2:
movs r3, #0x1f
ands r2, r2, r3
cmp r2, #10
blo 2f
adds r2, r2, #6
2:
lsls r2, r2, #8
adds r1, r1, r2
1:
__cl (FLAG_N | FLAG_Z | FLAG_C | FLAG_V)
uxtb r2, r1
movs r2, r2
bne 1f
__se FLAG_Z
1:
movs r3, #FLAG_N
tst r2, r3
beq 1f
__se FLAG_N
1:
lsrs r1, r1, #17
bcc 1f
__se FLAG_C
1:
mov r1, RA
eors r0, r1, r0
eors r1, r1, r2
ands r0, r0, r1
lsrs r0, r0, #8
bcc 1f
__se FLAG_V
mov RA, r2
adds PC, PC, #1
.endm
.macro _t a b