113 lines
3.1 KiB
Go
113 lines
3.1 KiB
Go
package cpu
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import (
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"fmt"
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"strings"
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"github.com/freewilll/apple2-go/mmu"
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)
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// printFlag prints a lower or uppercase letter depending on the state of the flag
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func printFlag(p byte, flag uint8, code string) {
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if (p & flag) == 0 {
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fmt.Print(code)
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} else {
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fmt.Printf("%s", strings.ToUpper(code))
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}
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}
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// printInstruction prings a single instruction and optionally also registers
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func printInstruction(instruction string, showRegisters bool) {
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fmt.Printf("%04x- %-24s", State.PC, instruction)
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if showRegisters {
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fmt.Printf(" A=%02x X=%02x Y=%02x S=%02x P=%02x ",
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State.A,
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State.X,
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State.Y,
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State.SP,
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State.P,
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)
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printFlag(State.P, cpuFlagN, "n")
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printFlag(State.P, cpuFlagV, "v")
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fmt.Print("-") // cpuFlagR flag that's always 1
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printFlag(State.P, cpuFlagB, "b")
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printFlag(State.P, cpuFlagD, "d")
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printFlag(State.P, cpuFlagI, "i")
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printFlag(State.P, cpuFlagZ, "z")
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printFlag(State.P, cpuFlagC, "c")
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}
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fmt.Println("")
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}
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// PrintInstruction prints the instruction at the current PC
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func PrintInstruction(showRegisters bool) {
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opcodeValue := mmu.ReadPageTable[(State.PC)>>8][(State.PC)&0xff]
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opcode := opCodes[opcodeValue]
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mnemonic := opcode.mnemonic
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size := opcode.addressingMode.operandSize
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stringFormat := opcode.addressingMode.stringFormat
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var value uint16
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if size == 0 {
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printInstruction(fmt.Sprintf("%02x %s", opcodeValue, mnemonic), showRegisters)
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return
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}
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var opcodes string
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var suffix string
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if opcode.addressingMode.mode == amRelative {
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value = uint16(mmu.ReadPageTable[(State.PC+1)>>8][(State.PC+1)&0xff])
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var relativeAddress uint16
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if (value & 0x80) == 0 {
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relativeAddress = State.PC + 2 + uint16(value)
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} else {
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relativeAddress = State.PC + 2 + uint16(value) - 0x100
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}
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suffix = fmt.Sprintf(stringFormat, relativeAddress)
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opcodes = fmt.Sprintf("%02x %02x ", opcodeValue, value)
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} else if size == 1 {
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value = uint16(mmu.ReadPageTable[(State.PC+1)>>8][(State.PC+1)&0xff])
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suffix = fmt.Sprintf(stringFormat, value)
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opcodes = fmt.Sprintf("%02x %02x ", opcodeValue, value)
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} else if size == 2 {
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lsb := mmu.ReadPageTable[(State.PC+1)>>8][(State.PC+1)&0xff]
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msb := mmu.ReadPageTable[(State.PC+2)>>8][(State.PC+2)&0xff]
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value = uint16(lsb) + uint16(msb)*0x100
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suffix = fmt.Sprintf(stringFormat, value)
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opcodes = fmt.Sprintf("%02x %02x %02x ", opcodeValue, lsb, msb)
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}
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printInstruction(fmt.Sprintf("%s %s %s", opcodes, mnemonic, suffix), showRegisters)
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}
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// AdvanceInstruction goes forward one instruction without executing anything
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func AdvanceInstruction() {
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opcodeValue := mmu.ReadPageTable[(State.PC)>>8][(State.PC)&0xff]
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opcode := opCodes[opcodeValue]
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size := opcode.addressingMode.operandSize + 1
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State.PC += uint16(size)
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}
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// DumpMemory dumps $100 bytes of memory
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func DumpMemory(offset uint16) {
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var i uint16
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for i = 0; i < 0x100; i++ {
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if (i & 0xf) == 8 {
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fmt.Print(" ")
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}
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if (i & 0xf) == 0 {
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if i > 0 {
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fmt.Print("\n")
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}
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fmt.Printf("%04x ", offset+i)
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}
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fmt.Printf(" %02x", mmu.ReadPageTable[(offset+i)>>8][(offset+i)&0xff])
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}
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fmt.Print("\n")
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}
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