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Take a swing at scanning versus not.

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This commit is contained in:
Thomas Harte
2025-09-16 22:29:00 -04:00
parent 18b32dbba3
commit d78f35b940
1 changed files with 34 additions and 13 deletions
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47
Machines/Acorn/BBCMicro/BBCMicro.cpp
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@@ -104,14 +104,17 @@ protected:
/*!
Models the system VIA, which connects to the SN76489 and the keyboard.
*/
struct SystemVIAPortHandler;
using SystemVIA = MOS::MOS6522::MOS6522<SystemVIAPortHandler>;
struct SystemVIAPortHandler: public MOS::MOS6522::IRQDelegatePortHandler {
SystemVIAPortHandler(Audio &audio, VideoBaseAddress &video_base) :
audio_(audio), video_base_(video_base)
SystemVIAPortHandler(Audio &audio, VideoBaseAddress &video_base, SystemVIA &via) :
audio_(audio), video_base_(video_base), via_(via)
{
// Set initial mode.
key_states_[7] = true;
key_states_[8] = true;
key_states_[9] = true;
unscanned_key_states_[7] = true;
unscanned_key_states_[8] = true;
unscanned_key_states_[9] = true;
}
// CA2: key pressed;
@@ -124,6 +127,7 @@ struct SystemVIAPortHandler: public MOS::MOS6522::IRQDelegatePortHandler {
if(port == MOS::MOS6522::Port::A) {
// Logger::info().append("Port A write: %02x", value);
port_a_output_ = value;
update_ca2();
return;
}
@@ -131,13 +135,17 @@ struct SystemVIAPortHandler: public MOS::MOS6522::IRQDelegatePortHandler {
//
// B0: enable writes to the sound generator;
// B1, B2: read/write to the sound processor;
// B3: enable writes to the keyboard.
// B3: keyboard scanning mode (?)
// B4/B5: "hardware scrolling" (new base address > 32768?)
// B6/B7: keyboard LEDs.
const auto mask = uint8_t(1 << (value & 7));
const auto old_latch = latch_;
latch_ = (latch_ & ~mask) | ((value & 8) ? mask : 0);
if(mask == 0x8) {
update_ca2();
}
// Check for a strobe on the audio output.
if((old_latch^latch_) & old_latch & 1) {
audio_->write(port_a_output_);
@@ -169,11 +177,12 @@ struct SystemVIAPortHandler: public MOS::MOS6522::IRQDelegatePortHandler {
// Read keyboard. Low six bits of output are key to check, state should be returned in high bit.
Logger::info().append("Keyboard read from key %d = %d", port_a_output_, bool(key_states_[port_a_output_ & 0x7f]));
return key_states_[port_a_output_ & 0x7f] ? 0x80 : 0x00;
return key_state() ? 0x80 : 0x00;
}
void set_key(const uint8_t key, const bool pressed) {
key_states_[key] = pressed;
update_ca2();
}
private:
@@ -183,9 +192,25 @@ private:
Audio &audio_;
VideoBaseAddress &video_base_;
SystemVIA &via_;
std::bitset<128> key_states_{};
std::bitset<128> unscanned_key_states_{};
/// @returns The state of the key currently selected by port A.
bool key_state() const {
return
unscanned_key_states_[port_a_output_ & 0x7f] |
key_states_[port_a_output_ & 0x7f];
}
void update_ca2() {
if(latch_ & 8) {
via_.set_control_line_input<MOS::MOS6522::Port::A, MOS::MOS6522::Line::Two>(key_states_.any());
} else {
via_.set_control_line_input<MOS::MOS6522::Port::A, MOS::MOS6522::Line::Two>(key_state());
}
}
};
using SystemVIA = MOS::MOS6522::MOS6522<SystemVIAPortHandler>;
/*!
Handles CRTC bus activity.
@@ -381,7 +406,7 @@ public:
const ROMMachine::ROMFetcher &rom_fetcher
) :
m6502_(*this),
system_via_port_handler_(audio_, crtc_bus_handler_),
system_via_port_handler_(audio_, crtc_bus_handler_, system_via_),
user_via_(user_via_port_handler_),
system_via_(system_via_port_handler_),
crtc_bus_handler_(ram_.data(), system_via_),
@@ -607,10 +632,6 @@ private:
void set_key_state(const uint16_t key, const bool is_pressed) override {
system_via_port_handler_.set_key(uint8_t(key), is_pressed);
// TODO: what's the actual input to CA2?
system_via_.set_control_line_input<MOS::MOS6522::Port::A, MOS::MOS6522::Line::Two>(true);
system_via_.set_control_line_input<MOS::MOS6522::Port::A, MOS::MOS6522::Line::Two>(false);
}
// MARK: - TimedMachine.