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Ensured counter-intuitive CRTC writes get through, taking the opportunity to correct my handling of port IO in general: selecting multiple devices for input results in a logical AND (i.e. open collector mode), and both the CRTC and gate array will receive data from 'input's if applicable.

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This commit is contained in:
Thomas Harte 2017-08-10 12:39:19 -04:00
parent 6a6e5ae79c
commit 4961fda2a9
1 changed files with 66 additions and 54 deletions
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120
Machines/AmstradCPC/AmstradCPC.cpp
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@ -579,48 +579,7 @@ class ConcreteMachine:
case CPU::Z80::PartialMachineCycle::Output:
// Check for a gate array access.
if((address & 0xc000) == 0x4000) {
switch(*cycle.value >> 6) {
case 0: crtc_bus_handler_.select_pen(*cycle.value & 0x1f); break;
case 1: crtc_bus_handler_.set_colour(*cycle.value & 0x1f); break;
case 2:
// Perform ROM paging.
read_pointers_[0] = (*cycle.value & 4) ? write_pointers_[0] : roms_[rom_model_].data();
upper_rom_is_paged_ = !(*cycle.value & 8);
read_pointers_[3] = upper_rom_is_paged_ ? roms_[upper_rom_].data() : write_pointers_[3];
// Reset the interrupt timer if requested.
if(*cycle.value & 0x10) interrupt_timer_.reset_count();
// Post the next mode.
crtc_bus_handler_.set_next_mode(*cycle.value & 3);
break;
case 3:
// Perform RAM paging, if 128kb is permitted.
if(has_128k_) {
bool adjust_low_read_pointer = read_pointers_[0] == write_pointers_[0];
bool adjust_high_read_pointer = read_pointers_[3] == write_pointers_[3];
#define RAM_BANK(x) &ram_[x * 16384]
#define RAM_CONFIG(a, b, c, d) write_pointers_[0] = RAM_BANK(a); write_pointers_[1] = RAM_BANK(b); write_pointers_[2] = RAM_BANK(c); write_pointers_[3] = RAM_BANK(d);
switch(*cycle.value & 7) {
case 0: RAM_CONFIG(0, 1, 2, 3); break;
case 1: RAM_CONFIG(0, 1, 2, 7); break;
case 2: RAM_CONFIG(4, 5, 6, 7); break;
case 3: RAM_CONFIG(0, 3, 2, 7); break;
case 4: RAM_CONFIG(0, 4, 2, 3); break;
case 5: RAM_CONFIG(0, 5, 2, 3); break;
case 6: RAM_CONFIG(0, 6, 2, 3); break;
case 7: RAM_CONFIG(0, 7, 2, 3); break;
}
#undef RAM_CONFIG
#undef RAM_BANK
if(adjust_low_read_pointer) read_pointers_[0] = write_pointers_[0];
read_pointers_[1] = write_pointers_[1];
read_pointers_[2] = write_pointers_[2];
if(adjust_high_read_pointer) read_pointers_[3] = write_pointers_[3];
}
break;
}
write_to_gate_array(*cycle.value);
}
// Check for an upper ROM selection
@ -634,7 +593,7 @@ class ConcreteMachine:
switch((address >> 8) & 3) {
case 0: crtc_.select_register(*cycle.value); break;
case 1: crtc_.set_register(*cycle.value); break;
case 2: case 3: printf("Illegal CRTC write?\n"); break;
default: break;
}
}
@ -657,23 +616,31 @@ class ConcreteMachine:
// Default to nothing answering
*cycle.value = 0xff;
// Check for a CRTC access
if(!(address & 0x4000)) {
switch((address >> 8) & 3) {
case 0: case 1: printf("Illegal CRTC read?\n"); break;
case 2: *cycle.value = crtc_.get_status(); break;
case 3: *cycle.value = crtc_.get_register(); break;
}
}
// Check for a PIO access
if(!(address & 0x800)) {
*cycle.value = i8255_.get_register((address >> 8) & 3);
*cycle.value &= i8255_.get_register((address >> 8) & 3);
}
// Check for an FDC access
if(has_fdc_ && (address & 0x580) == 0x100) {
*cycle.value = fdc_.get_register(address & 1);
*cycle.value &= fdc_.get_register(address & 1);
}
// Check for a CRTC access; the below is not a typo — the CRTC can be selected
// for writing via an input, and will sample whatever happens to be available
if(!(address & 0x4000)) {
switch((address >> 8) & 3) {
case 0: crtc_.select_register(*cycle.value); break;
case 1: crtc_.set_register(*cycle.value); break;
case 2: *cycle.value &= crtc_.get_status(); break;
case 3: *cycle.value &= crtc_.get_register(); break;
}
}
// As with the CRTC, the gate array will sample the bus if the address decoding
// implies that it should, unaware of data direction
if((address & 0xc000) == 0x4000) {
write_to_gate_array(*cycle.value);
}
break;
@ -794,6 +761,51 @@ class ConcreteMachine:
}
private:
inline void write_to_gate_array(uint8_t value) {
switch(value >> 6) {
case 0: crtc_bus_handler_.select_pen(value & 0x1f); break;
case 1: crtc_bus_handler_.set_colour(value & 0x1f); break;
case 2:
// Perform ROM paging.
read_pointers_[0] = (value & 4) ? write_pointers_[0] : roms_[rom_model_].data();
upper_rom_is_paged_ = !(value & 8);
read_pointers_[3] = upper_rom_is_paged_ ? roms_[upper_rom_].data() : write_pointers_[3];
// Reset the interrupt timer if requested.
if(value & 0x10) interrupt_timer_.reset_count();
// Post the next mode.
crtc_bus_handler_.set_next_mode(value & 3);
break;
case 3:
// Perform RAM paging, if 128kb is permitted.
if(has_128k_) {
bool adjust_low_read_pointer = read_pointers_[0] == write_pointers_[0];
bool adjust_high_read_pointer = read_pointers_[3] == write_pointers_[3];
#define RAM_BANK(x) &ram_[x * 16384]
#define RAM_CONFIG(a, b, c, d) write_pointers_[0] = RAM_BANK(a); write_pointers_[1] = RAM_BANK(b); write_pointers_[2] = RAM_BANK(c); write_pointers_[3] = RAM_BANK(d);
switch(value & 7) {
case 0: RAM_CONFIG(0, 1, 2, 3); break;
case 1: RAM_CONFIG(0, 1, 2, 7); break;
case 2: RAM_CONFIG(4, 5, 6, 7); break;
case 3: RAM_CONFIG(0, 3, 2, 7); break;
case 4: RAM_CONFIG(0, 4, 2, 3); break;
case 5: RAM_CONFIG(0, 5, 2, 3); break;
case 6: RAM_CONFIG(0, 6, 2, 3); break;
case 7: RAM_CONFIG(0, 7, 2, 3); break;
}
#undef RAM_CONFIG
#undef RAM_BANK
if(adjust_low_read_pointer) read_pointers_[0] = write_pointers_[0];
read_pointers_[1] = write_pointers_[1];
read_pointers_[2] = write_pointers_[2];
if(adjust_high_read_pointer) read_pointers_[3] = write_pointers_[3];
}
break;
}
}
CPU::Z80::Processor<ConcreteMachine> z80_;
CRTCBusHandler crtc_bus_handler_;