99 lines
1.9 KiB
Go
99 lines
1.9 KiB
Go
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package main
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import (
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"log"
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"github.com/koron-go/z80"
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)
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// ioPeripheral is a z80.IO device at a given address.
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type ioPeripheral struct {
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start uint8
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length uint8
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peripheral z80.IO
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}
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// ioArbiter is a collection of I/O devices at addresses. It implements z80.IO
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// itself, dispatching to the appropriate device as needed.
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type ioArbiter struct {
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peripherals []*ioPeripheral
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}
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func (i *ioArbiter) get(addr uint8) *ioPeripheral {
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for _, periph := range i.peripherals {
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if addr < periph.start {
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continue
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}
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if addr > periph.start+periph.length {
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continue
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}
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return periph
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}
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return nil
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}
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func (i *ioArbiter) In(addr uint8) uint8 {
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p := i.get(addr)
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if p == nil {
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log.Fatalf("Unhandled I/O In at %02x", addr)
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return 0
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}
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return p.peripheral.In(addr - p.start)
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}
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func (i *ioArbiter) Out(addr uint8, value uint8) {
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p := i.get(addr)
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if p == nil {
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log.Fatalf("Unhandled I/O Out at %02x", addr)
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return
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}
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p.peripheral.Out(addr-p.start, value)
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}
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// memory is a continuous memory region at a given address, optionally marked
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// read only.
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type memory struct {
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start uint16
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data []uint8
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readonly bool
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}
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// memoryArbiter implements Z80.Memory and dispatches accesses to subordinate
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// memory instances.
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type memoryArbiter struct {
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memories []memory
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}
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func (m *memoryArbiter) get(addr uint16) *memory {
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for _, mem := range m.memories {
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if addr < mem.start {
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continue
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}
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if addr >= mem.start+uint16(len(mem.data)) {
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continue
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}
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return &mem
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}
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return nil
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}
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func (m *memoryArbiter) Get(addr uint16) uint8 {
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mem := m.get(addr)
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if mem == nil {
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log.Fatalf("Unhandled memory Get at %04x", addr)
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return 0
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}
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return mem.data[addr-mem.start]
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}
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func (m *memoryArbiter) Set(addr uint16, value uint8) {
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mem := m.get(addr)
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if mem == nil {
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log.Fatalf("Unhandled memory Set at %04x", addr)
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return
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}
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if mem.readonly {
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log.Fatalf("Read-only memory Set at %04x", addr)
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}
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mem.data[addr-mem.start] = value
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}
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