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Merge pull request #1298 from TomHarte/CRTC16bit

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Make CRTC model part of type.
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Thomas Harte 2024-01-01 22:57:29 -05:00 committed by GitHub
commit 2db83acb98
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4 changed files with 43 additions and 30 deletions
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52
Components/6845/CRTC6845.hpp
View File

@ -46,19 +46,21 @@ class BusHandler {
void perform_bus_cycle_phase2(const BusState &) {}
};
enum Personality {
enum class Personality {
HD6845S, // Type 0 in CPC parlance. Zero-width HSYNC available, no status, programmable VSYNC length.
// Considered exactly identical to the UM6845, so this enum covers both.
UM6845R, // Type 1 in CPC parlance. Status register, fixed-length VSYNC.
MC6845, // Type 2. No status register, fixed-length VSYNC, no zero-length HSYNC.
AMS40226 // Type 3. Status is get register, fixed-length VSYNC, no zero-length HSYNC.
AMS40226, // Type 3. Status is get register, fixed-length VSYNC, no zero-length HSYNC.
EGA, // Extended EGA-style CRTC; uses 16-bit addressing throughout.
};
// https://www.pcjs.org/blog/2018/03/20/ advises that "the behavior of bits 5 and 6 [of register 10, the cursor start
// register is really card specific".
//
// This enum captures those specifics.
enum CursorType {
enum class CursorType {
/// No cursor signal is generated.
None,
/// MDA style: 00 => symmetric blinking; 01 or 10 => no blinking; 11 => short on, long off.
@ -69,21 +71,20 @@ enum CursorType {
// TODO UM6845R and R12/R13; see http://www.cpcwiki.eu/index.php/CRTC#CRTC_Differences
template <class T, CursorType cursor_type> class CRTC6845 {
template <class BusHandlerT, Personality personality, CursorType cursor_type> class CRTC6845 {
public:
CRTC6845(Personality p, T &bus_handler) noexcept :
personality_(p), bus_handler_(bus_handler), status_(0) {}
CRTC6845(BusHandlerT &bus_handler) noexcept :
bus_handler_(bus_handler), status_(0) {}
void select_register(uint8_t r) {
selected_register_ = r;
}
uint8_t get_status() {
switch(personality_) {
case UM6845R: return status_ | (bus_state_.vsync ? 0x20 : 0x00);
case AMS40226: return get_register();
default: return 0xff;
switch(personality) {
case Personality::UM6845R: return status_ | (bus_state_.vsync ? 0x20 : 0x00);
case Personality::AMS40226: return get_register();
default: return 0xff;
}
return 0xff;
}
@ -92,7 +93,7 @@ template <class T, CursorType cursor_type> class CRTC6845 {
if(selected_register_ == 31) status_ &= ~0x80;
if(selected_register_ == 16 || selected_register_ == 17) status_ &= ~0x40;
if(personality_ == UM6845R && selected_register_ == 31) return dummy_register_;
if(personality == Personality::UM6845R && selected_register_ == 31) return dummy_register_;
if(selected_register_ < 12 || selected_register_ > 17) return 0xff;
return registers_[selected_register_];
}
@ -100,11 +101,13 @@ template <class T, CursorType cursor_type> class CRTC6845 {
void set_register(uint8_t value) {
static constexpr uint8_t masks[] = {
0xff, 0xff, 0xff, 0xff, 0x7f, 0x1f, 0x7f, 0x7f,
0xff, 0x1f, 0x7f, 0x1f, 0x3f, 0xff, 0x3f, 0xff
0xff, 0x1f, 0x7f, 0x1f,
uint8_t(RefreshMask >> 8), uint8_t(RefreshMask),
uint8_t(RefreshMask >> 8), uint8_t(RefreshMask),
};
// Per CPC documentation, skew doesn't work on a "type 1 or 2", i.e. an MC6845 or a UM6845R.
if(selected_register_ == 8 && personality_ != UM6845R && personality_ != MC6845) {
if(selected_register_ == 8 && personality != Personality::UM6845R && personality != Personality::MC6845) {
switch((value >> 4)&3) {
default: display_skew_mask_ = 1; break;
case 1: display_skew_mask_ = 2; break;
@ -115,7 +118,7 @@ template <class T, CursorType cursor_type> class CRTC6845 {
if(selected_register_ < 16) {
registers_[selected_register_] = value & masks[selected_register_];
}
if(selected_register_ == 31 && personality_ == UM6845R) {
if(selected_register_ == 31 && personality == Personality::UM6845R) {
dummy_register_ = value;
}
}
@ -137,7 +140,7 @@ template <class T, CursorType cursor_type> class CRTC6845 {
}
perform_bus_cycle_phase1();
bus_state_.refresh_address = (bus_state_.refresh_address + 1) & 0x3fff;
bus_state_.refresh_address = (bus_state_.refresh_address + 1) & RefreshMask;
bus_state_.cursor = is_cursor_line_ &&
bus_state_.refresh_address == (registers_[15] | (registers_[14] << 8));
@ -162,9 +165,9 @@ template <class T, CursorType cursor_type> class CRTC6845 {
// cancellation of the plan to perform sync if this is an HD6845S or UM6845R; otherwise zero
// will end up counting as 16 as it won't be checked until after overflow.
if(bus_state_.hsync) {
switch(personality_) {
case HD6845S:
case UM6845R:
switch(personality) {
case Personality::HD6845S:
case Personality::UM6845R:
bus_state_.hsync = hsync_counter_ != (registers_[3] & 15);
hsync_counter_ = (hsync_counter_ + 1) & 15;
break;
@ -184,6 +187,8 @@ template <class T, CursorType cursor_type> class CRTC6845 {
}
private:
static constexpr uint16_t RefreshMask = (personality >= Personality::EGA) ? 0xffff : 0x3fff;
inline void perform_bus_cycle_phase1() {
// Skew theory of operation: keep a history of the last three states, and apply whichever is selected.
character_is_visible_shifter_ = (character_is_visible_shifter_ << 1) | unsigned(character_is_visible_);
@ -207,9 +212,9 @@ template <class T, CursorType cursor_type> class CRTC6845 {
vsync_counter_ = (vsync_counter_ + 1) & 15;
// On the UM6845R and AMS40226, honour the programmed vertical sync time; on the other CRTCs
// always use a vertical sync count of 16.
switch(personality_) {
case HD6845S:
case AMS40226:
switch(personality) {
case Personality::HD6845S:
case Personality::AMS40226:
bus_state_.vsync = vsync_counter_ != (registers_[3] >> 4);
break;
default:
@ -290,8 +295,7 @@ template <class T, CursorType cursor_type> class CRTC6845 {
++bus_state_.field_count;
}
Personality personality_;
T &bus_handler_;
BusHandlerT &bus_handler_;
BusState bus_state_;
uint8_t registers_[18] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};

7
Machines/AmstradCPC/AmstradCPC.cpp
View File

@ -583,7 +583,10 @@ class CRTCBusHandler {
InterruptTimer &interrupt_timer_;
};
using CRTC = Motorola::CRTC::CRTC6845<CRTCBusHandler, Motorola::CRTC::CursorType::None>;
using CRTC = Motorola::CRTC::CRTC6845<
CRTCBusHandler,
Motorola::CRTC::Personality::HD6845S,
Motorola::CRTC::CursorType::None>;
/*!
Holds and vends the current keyboard state, acting as the AY's port handler.
@ -766,7 +769,7 @@ template <bool has_fdc> class ConcreteMachine:
ConcreteMachine(const Analyser::Static::AmstradCPC::Target &target, const ROMMachine::ROMFetcher &rom_fetcher) :
z80_(*this),
crtc_bus_handler_(ram_, interrupt_timer_),
crtc_(Motorola::CRTC::HD6845S, crtc_bus_handler_),
crtc_(crtc_bus_handler_),
i8255_port_handler_(key_state_, crtc_, ay_, tape_player_),
i8255_(i8255_port_handler_),
tape_player_(8000000),

7
Machines/PCCompatible/CGA.hpp
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@ -17,7 +17,7 @@ namespace PCCompatible {
class CGA {
public:
CGA() : crtc_(Motorola::CRTC::Personality::HD6845S, outputter_) {}
CGA() : crtc_(outputter_) {}
static constexpr uint32_t BaseAddress = 0xb'8000;
static constexpr auto FontROM = ROM::Name::PCCompatibleCGAFont;
@ -439,7 +439,10 @@ class CGA {
return (source & 0x10) ? bright(result) : yellow_to_brown(result);
}
} outputter_;
Motorola::CRTC::CRTC6845<CRTCOutputter, Motorola::CRTC::CursorType::MDA> crtc_;
Motorola::CRTC::CRTC6845<
CRTCOutputter,
Motorola::CRTC::Personality::HD6845S,
Motorola::CRTC::CursorType::MDA> crtc_;
int full_clock_ = 0;

7
Machines/PCCompatible/MDA.hpp
View File

@ -17,7 +17,7 @@ namespace PCCompatible {
class MDA {
public:
MDA() : crtc_(Motorola::CRTC::Personality::HD6845S, outputter_) {}
MDA() : crtc_(outputter_) {}
static constexpr uint32_t BaseAddress = 0xb'0000;
static constexpr auto FontROM = ROM::Name::PCCompatibleMDAFont;
@ -226,7 +226,10 @@ class MDA {
uint8_t control_ = 0;
} outputter_;
Motorola::CRTC::CRTC6845<CRTCOutputter, Motorola::CRTC::CursorType::MDA> crtc_;
Motorola::CRTC::CRTC6845<
CRTCOutputter,
Motorola::CRTC::Personality::HD6845S,
Motorola::CRTC::CursorType::MDA> crtc_;
int full_clock_ = 0;
};