mirror of
https://github.com/ivanizag/izapple2.git
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93 lines
2.0 KiB
Go
93 lines
2.0 KiB
Go
package core6502
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import "fmt"
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const (
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regA = 0
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regX = 1
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regY = 2
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regP = 3
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regSP = 4
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regPC = 5 // 2 bytes
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regPC2 = 6
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regNone = -1
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)
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const (
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flagN uint8 = 1 << 7
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flagV uint8 = 1 << 6
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flag5 uint8 = 1 << 5
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flagB uint8 = 1 << 4
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flagD uint8 = 1 << 3
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flagI uint8 = 1 << 2
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flagZ uint8 = 1 << 1
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flagC uint8 = 1 << 0
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)
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type registers struct {
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data [7]uint8
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}
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func (r *registers) getRegister(i int) uint8 { return r.data[i] }
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func (r *registers) getA() uint8 { return r.data[regA] }
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func (r *registers) getX() uint8 { return r.data[regX] }
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func (r *registers) getY() uint8 { return r.data[regY] }
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func (r *registers) getP() uint8 { return r.data[regP] }
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func (r *registers) getSP() uint8 { return r.data[regSP] }
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func (r *registers) setRegister(i int, v uint8) {
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r.data[i] = v
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}
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func (r *registers) setA(v uint8) { r.setRegister(regA, v) }
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func (r *registers) setX(v uint8) { r.setRegister(regX, v) }
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func (r *registers) setY(v uint8) { r.setRegister(regY, v) }
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func (r *registers) setP(v uint8) { r.setRegister(regP, v) }
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func (r *registers) setSP(v uint8) { r.setRegister(regSP, v) }
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func (r *registers) getPC() uint16 {
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return uint16(r.data[regPC])*256 + uint16(r.data[regPC2])
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}
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func (r *registers) setPC(v uint16) {
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r.data[regPC] = uint8(v >> 8)
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r.data[regPC2] = uint8(v)
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}
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func (r *registers) getFlagBit(i uint8) uint8 {
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if r.getFlag(i) {
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return 1
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}
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return 0
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}
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func (r *registers) getFlag(i uint8) bool {
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return (r.data[regP] & i) != 0
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}
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func (r *registers) setFlag(i uint8) {
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r.data[regP] |= i
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}
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func (r *registers) clearFlag(i uint8) {
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r.data[regP] &^= i
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}
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func (r *registers) updateFlag(i uint8, v bool) {
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if v {
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r.setFlag(i)
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} else {
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r.clearFlag(i)
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}
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}
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func (r *registers) updateFlagZN(t uint8) {
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r.updateFlag(flagZ, t == 0)
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r.updateFlag(flagN, t >= (1<<7))
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}
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func (r registers) String() string {
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return fmt.Sprintf("A: %#02x, X: %#02x, Y: %#02x, SP: %#02x, PC: %#04x, P: %#02x, (NV-BDIZC): %08b",
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r.getA(), r.getX(), r.getY(), r.getSP(), r.getPC(), r.getP(), r.getP())
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}
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