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Adds a hard-coded value sufficient to advance in TOS startup.

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Thomas Harte 2019-04-06 20:00:34 -04:00
parent 03f365e696
commit 0af57806da
1 changed files with 23 additions and 3 deletions
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26
OSBindings/Mac/Clock SignalTests/EmuTOSTests.mm
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@ -30,13 +30,15 @@ class EmuTOS: public CPU::MC68000::BusHandler {
}
HalfCycles perform_bus_operation(const CPU::MC68000::Microcycle &cycle, int is_supervisor) {
uint32_t word_address = cycle.word_address();
const uint32_t address = cycle.word_address();
uint32_t word_address = address;
// As much about the Atari ST's memory map as is relevant here: the ROM begins
// at 0xfc0000, and the first eight bytes are mirrored to the first four memory
// addresses in order for /RESET to work properly. RAM otherwise fills the first
// 512kb of the address space. Trying to write to ROM raises a bus error.
const bool is_peripheral = word_address > (0xff0000 >> 1);
const bool is_rom = word_address > (0xfc0000 >> 1) || word_address < 4;
uint16_t *const base = is_rom ? emuTOS_.data() : ram_.data();
if(is_rom) {
@ -47,14 +49,32 @@ class EmuTOS: public CPU::MC68000::BusHandler {
using Microcycle = CPU::MC68000::Microcycle;
if(cycle.data_select_active()) {
uint16_t peripheral_result = 0xffff;
if(is_peripheral) {
switch(address & 0x7ff) {
// A hard-coded value for TIMER B.
case (0xa21 >> 1):
peripheral_result = 0x00000001;
break;
}
printf("Peripheral: %c %08x", (cycle.operation & Microcycle::Read) ? 'r' : 'w', *cycle.address);
if(!(cycle.operation & Microcycle::Read)) {
if(cycle.operation & Microcycle::SelectByte)
printf(" %02x", cycle.value->halves.low);
else
printf(" %04x", cycle.value->full);
}
printf("\n");
}
switch(cycle.operation & (Microcycle::SelectWord | Microcycle::SelectByte | Microcycle::Read)) {
default: break;
case Microcycle::SelectWord | Microcycle::Read:
cycle.value->full = base[word_address];
cycle.value->full = is_peripheral ? peripheral_result : base[word_address];
break;
case Microcycle::SelectByte | Microcycle::Read:
cycle.value->halves.low = base[word_address] >> cycle.byte_shift();
cycle.value->halves.low = (is_peripheral ? peripheral_result : base[word_address]) >> cycle.byte_shift();
break;
case Microcycle::SelectWord:
base[word_address] = cycle.value->full;