mirror of https://github.com/ariejan/i6502.git
54 lines
1.4 KiB
Go
54 lines
1.4 KiB
Go
package i6502
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import (
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"fmt"
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)
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type Instruction struct {
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// Embed OpType
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OpType
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// 8-bit operand for 2-byte instructions
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Op8 byte
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// 16-bit operand for 3-byte instructions
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Op16 uint16
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// Address location where this instruction got read
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Address uint16
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}
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func (i Instruction) String() (output string) {
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switch i.Size {
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case 1:
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output = fmt.Sprintf("~~~ 0x%04X: 0x%02X - %s [%s] {%d}\n", i.Address, i.Opcode, instructionNames[i.opcodeId], addressingNames[i.addressingId], i.Cycles)
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case 2:
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output = fmt.Sprintf("~~~ 0x%04X: 0x%02X - %s 0x%02X [%s] {%d}\n", i.Address, i.Opcode, instructionNames[i.opcodeId], i.Op8, addressingNames[i.addressingId], i.Cycles)
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case 3:
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output = fmt.Sprintf("~~~ 0x%04X: 0x%02X - %s 0x%04X [%s] {%d}\n", i.Address, i.Opcode, instructionNames[i.opcodeId], i.Op16, addressingNames[i.addressingId], i.Cycles)
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}
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return
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}
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func (c *Cpu) readNextInstruction() Instruction {
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// Read the opcode
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opcode := c.bus.Read(c.PC)
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optype, ok := opTypes[opcode]
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if !ok {
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panic(fmt.Sprintf("Unknown or unimplemented opcode 0x%02X\n%s", opcode, c.String()))
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}
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instruction := Instruction{OpType: optype, Address: c.PC}
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switch instruction.Size {
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case 1: // Zero operand instruction
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case 2: // 8-bit operand
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instruction.Op8 = c.bus.Read(c.PC + 1)
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case 3: // 16-bit operand
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instruction.Op16 = c.bus.Read16(c.PC + 1)
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}
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return instruction
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}
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