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Merge pull request #183 from TomHarte/6845Address

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Corrects 6845 address loading
This commit is contained in:
Thomas Harte 2017-08-10 12:51:40 -04:00 committed by GitHub
commit f258d6fbb2
2 changed files with 99 additions and 70 deletions
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47
Components/6845/CRTC6845.hpp
View File

@ -31,9 +31,18 @@ class BusHandler {
void perform_bus_cycle(const BusState &) {}
};
enum Personality {
HD6845S, //
UM6845R, //
MC6845, //
AMS40226 //
};
template <class T> class CRTC6845 {
public:
CRTC6845(T &bus_handler) : bus_handler_(bus_handler) {}
CRTC6845(Personality p, T &bus_handler) :
personality_(p), bus_handler_(bus_handler) {}
void run_for(Cycles cycles) {
int cyles_remaining = cycles.as_int();
@ -58,22 +67,18 @@ template <class T> class CRTC6845 {
if(hsync_down_counter_) bus_state_.hsync = true;
}
// update refresh address
if(character_is_visible_) {
bus_state_.refresh_address++;
}
// check for end of visible characters
if(character_counter_ == registers_[1]) {
bus_state_.refresh_address++;
character_is_visible_ = false;
} else {
// update refresh address
if(character_is_visible_) {
bus_state_.refresh_address++;
}
}
// check for end-of-line
if(is_end_of_line) {
character_counter_ = 0;
character_is_visible_ = true;
// check for end of vertical sync
if(vsync_down_counter_) {
vsync_down_counter_--;
@ -94,7 +99,8 @@ template <class T> class CRTC6845 {
} else {
// advance vertical counter
if(bus_state_.row_address == registers_[9]) {
line_address_ = bus_state_.refresh_address;
if(!character_is_visible_)
line_address_ = bus_state_.refresh_address;
bus_state_.row_address = 0;
bool is_at_end_of_frame = line_counter_ == registers_[4];
@ -126,9 +132,12 @@ template <class T> class CRTC6845 {
}
} else {
bus_state_.row_address++;
bus_state_.refresh_address = line_address_;
}
bus_state_.refresh_address = line_address_;
}
character_counter_ = 0;
character_is_visible_ = true;
}
bus_state_.display_enable = character_is_visible_ && line_is_visible_;
@ -137,7 +146,7 @@ template <class T> class CRTC6845 {
}
void select_register(uint8_t r) {
selected_register_ = (int)r & 15;
selected_register_ = r;
}
uint8_t get_status() {
@ -145,18 +154,26 @@ template <class T> class CRTC6845 {
}
uint8_t get_register() {
if(selected_register_ < 12 || selected_register_ > 17) return 0xff;
return registers_[selected_register_];
}
void set_register(uint8_t value) {
registers_[selected_register_] = value;
static uint8_t masks[] = {
0xff, 0xff, 0xff, 0xff, 0x7f, 0x1f, 0x7f, 0x7f,
0xff, 0x1f, 0x7f, 0x1f, 0x3f, 0xff, 0x3f, 0xff
};
if(selected_register_ < 16)
registers_[selected_register_] = value & masks[selected_register_];
}
private:
Personality personality_;
T &bus_handler_;
BusState bus_state_;
uint8_t registers_[16];
uint8_t registers_[18];
int selected_register_;
uint8_t character_counter_;

122
Machines/AmstradCPC/AmstradCPC.cpp
View File

@ -528,7 +528,7 @@ class ConcreteMachine:
ConcreteMachine() :
z80_(*this),
crtc_counter_(HalfCycles(4)), // This starts the CRTC exactly out of phase with the memory accesses
crtc_(crtc_bus_handler_),
crtc_(Motorola::CRTC::HD6845S, crtc_bus_handler_),
crtc_bus_handler_(ram_, interrupt_timer_),
i8255_(i8255_port_handler_),
i8255_port_handler_(key_state_, crtc_bus_handler_, ay_, tape_player_),
@ -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_;