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fixes

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This commit is contained in:
Irmen de Jong 2019-09-05 01:38:05 +02:00
parent 900c2aea23
commit e46982f652
1 changed files with 21 additions and 18 deletions
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19
sim65/src/components/Cpu6502.kt
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@ -16,8 +16,11 @@ interface ICpu {
val totalCycles: Int val totalCycles: Int
} }
// TODO: add additional cycles to certain instructions and addressing modes // TODO: add the optional additional cycles to certain instructions and addressing modes
// TODO: fix sbc and adc with BCD arithmetic. // TODO: fix sbc and adc with BCD arithmetic.
// TODO: add IRQ and NMI signaling.
// TODO: make a 65c02 variant as well (and re-enable the unit tests for that).
class Cpu6502(private val illegalInstrsAllowed: Boolean) : BusComponent(), ICpu { class Cpu6502(private val illegalInstrsAllowed: Boolean) : BusComponent(), ICpu {
override var tracing: Boolean = false override var tracing: Boolean = false
@ -700,10 +703,10 @@ class Cpu6502(private val illegalInstrsAllowed: Boolean) : BusComponent(), ICpu
if (lo and 0xff > 9) lo += 6 if (lo and 0xff > 9) lo += 6
var hi = (A shr 4) + (operand shr 4) + if (lo > 15) 1 else 0 var hi = (A shr 4) + (operand shr 4) + if (lo > 15) 1 else 0
if (hi and 0xff > 9) hi += 6 if (hi and 0xff > 9) hi += 6
var result = lo and 0x0f or (hi shl 4) val result = lo and 0x0f or (hi shl 4)
result = result and 0xff A = result and 0xff
Status.C = hi > 15 Status.C = hi > 15
Status.Z = result == 0 Status.Z = A == 0
Status.V = false // BCD never sets overflow flag Status.V = false // BCD never sets overflow flag
Status.N = false // BCD is never negative on NMOS 6502 (bug) Status.N = false // BCD is never negative on NMOS 6502 (bug)
} else { } else {
@ -991,10 +994,10 @@ class Cpu6502(private val illegalInstrsAllowed: Boolean) : BusComponent(), ICpu
if (Status.D) { if (Status.D) {
var lo = (A and 0x0f) - (operand and 0x0f) - if (Status.C) 0 else 1 var lo = (A and 0x0f) - (operand and 0x0f) - if (Status.C) 0 else 1
if (lo and 0x10 != 0) lo -= 6 if (lo and 0x10 != 0) lo -= 6
var h = (A shr 4) - (operand shr 4) - if (lo and 0x10 != 0) 1 else 0 var hi = (A shr 4) - (operand shr 4) - if (lo and 0x10 != 0) 1 else 0
if (h and 0x10 != 0) h -= 6 if (hi and 0x10 != 0) hi -= 6
val result = lo and 0x0f or ((h shl 4) and 0xff) val result = lo and 0x0f or ((hi shl 4) and 0xff)
Status.C = h and 255 < 15 Status.C = hi and 255 < 15
Status.Z = result == 0 Status.Z = result == 0
Status.V = false // BCD never sets overflow flag Status.V = false // BCD never sets overflow flag
Status.N = false // BCD is never negative on NMOS 6502 (bug) Status.N = false // BCD is never negative on NMOS 6502 (bug)