Apple-2-Tools
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izapple2
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Added INX, INY, DEX, DEY

This commit is contained in:
Ivan Izaguirre 2019-01-27 20:15:28 +01:00
parent d376e46596
commit de72112f90
1 changed files with 35 additions and 10 deletions
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45
execute.go
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@ -39,7 +39,21 @@ func opNOP(s *state, line []uint8, opcode opcode) {}
func buildOPTransfer(regSrc int, regDst int) opFunc {
return func(s *state, line []uint8, opcode opcode) {
s.registers.setRegister(regDst, s.registers.getRegister(regSrc))
value := s.registers.getRegister(regSrc)
s.registers.setRegister(regDst, value)
// TODO: Update flags (N, Z)
}
}
func buildOpIncDecRegister(reg int, inc bool) opFunc {
return func(s *state, line []uint8, opcode opcode) {
value := s.registers.getRegister(reg) + 1
if inc {
value++
} else {
value--
}
s.registers.setRegister(reg, value)
// TODO: Update flags (N, Z) for all but TXS
}
}
@ -85,24 +99,25 @@ func buildOpLoad(addressMode int, regDst int) opFunc {
}
var opcodes = [256]opcode{
0x00: opcode{"BRK", 1, 7, opNOP},
0x88: opcode{"DEY", 1, 2, buildOpIncDecRegister(regY, false)},
0x8A: opcode{"TXA", 1, 2, buildOPTransfer(regX, regA)},
0x98: opcode{"TYA", 1, 2, buildOPTransfer(regY, regA)},
0x9A: opcode{"TXS", 1, 2, buildOPTransfer(regX, regSP)},
0xA0: opcode{"LDY", 2, 2, buildOpLoad(modeImmediate, regY)},
0xA1: opcode{"LDX", 2, 6, buildOpLoad(modeIndexedIndirectX, regA)},
0xA2: opcode{"LDX", 2, 2, buildOpLoad(modeImmediate, regX)},
0xA4: opcode{"LDY", 2, 3, buildOpLoad(modeZeroPage, regY)},
0xA5: opcode{"LDA", 2, 3, buildOpLoad(modeZeroPage, regA)},
0xA6: opcode{"LDX", 2, 3, buildOpLoad(modeZeroPage, regX)},
0xA9: opcode{"LDA", 2, 2, buildOpLoad(modeImmediate, regA)},
0xAA: opcode{"TAX", 1, 2, buildOPTransfer(regA, regX)},
0xA8: opcode{"TAY", 1, 2, buildOPTransfer(regA, regY)},
0xBA: opcode{"TSX", 1, 2, buildOPTransfer(regSP, regX)},
0x8A: opcode{"TXA", 1, 2, buildOPTransfer(regX, regA)},
0x9A: opcode{"TXS", 1, 2, buildOPTransfer(regX, regSP)},
0x98: opcode{"TYA", 1, 2, buildOPTransfer(regY, regA)},
0xA9: opcode{"LDA", 2, 2, buildOpLoad(modeImmediate, regA)},
0xAA: opcode{"TAX", 1, 2, buildOPTransfer(regA, regX)},
0xAC: opcode{"LDY", 3, 4, buildOpLoad(modeAbsolute, regY)},
0xAD: opcode{"LDA", 3, 4, buildOpLoad(modeAbsolute, regA)},
@ -115,9 +130,19 @@ var opcodes = [256]opcode{
0xB6: opcode{"LDX", 2, 4, buildOpLoad(modeZeroPageY, regX)},
0xB9: opcode{"LDA", 3, 4, buildOpLoad(modeAbsoluteY, regA)}, // Extra cycles
0xBA: opcode{"TSX", 1, 2, buildOPTransfer(regSP, regX)},
0xBC: opcode{"LDY", 3, 4, buildOpLoad(modeAbsoluteX, regY)}, // Extra cycles
0xBD: opcode{"LDA", 3, 4, buildOpLoad(modeAbsoluteX, regA)}, // Extra cycles
0xBE: opcode{"LDX", 3, 4, buildOpLoad(modeAbsoluteY, regX)}, // Extra cycles
0xC8: opcode{"INY", 1, 2, buildOpIncDecRegister(regY, true)},
0xCA: opcode{"DEX", 1, 2, buildOpIncDecRegister(regX, false)},
0xE8: opcode{"INX", 1, 2, buildOpIncDecRegister(regX, true)},
0xEA: opcode{"NOP", 1, 2, opNOP},
}
func executeLine(s *state, line []uint8) {