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Merge pull request #488 from TomHarte/AYClarification

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Removes unused AY state and implements AND output readback.
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Thomas Harte 2018-06-26 19:31:50 -04:00 committed by GitHub
commit 5b88207477
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2 changed files with 13 additions and 12 deletions
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24
Components/AY38910/AY38910.cpp
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@ -225,14 +225,10 @@ uint8_t AY38910::get_register_value() {
};
if(selected_register_ > 15) return 0xff;
switch(selected_register_) {
default: return registers_[selected_register_] & register_masks[selected_register_];
case 14: return (registers_[0x7] & 0x40) ? registers_[14] : port_inputs_[0];
case 15: return (registers_[0x7] & 0x80) ? registers_[15] : port_inputs_[1];
}
return registers_[selected_register_] & register_masks[selected_register_];
}
// MARK: - Port handling
// MARK: - Port querying
uint8_t AY38910::get_port_output(bool port_b) {
return registers_[port_b ? 15 : 14];
@ -250,11 +246,16 @@ void AY38910::set_data_input(uint8_t r) {
}
uint8_t AY38910::get_data_output() {
if(control_state_ == Read && selected_register_ >= 14) {
if(port_handler_) {
return port_handler_->get_port_input(selected_register_ == 15);
} else {
return 0xff;
if(control_state_ == Read && selected_register_ >= 14 && selected_register_ < 16) {
// Per http://cpctech.cpc-live.com/docs/psgnotes.htm if a port is defined as output then the
// value returned to the CPU when reading it is the and of the output value and any input.
// If it's defined as input then you just get the input.
const uint8_t mask = port_handler_ ? port_handler_->get_port_input(selected_register_ == 15) : 0xff;
switch(selected_register_) {
default: break;
case 14: return mask & ((registers_[0x7] & 0x40) ? registers_[14] : 0xff);
case 15: return mask & ((registers_[0x7] & 0x80) ? registers_[15] : 0xff);
}
}
return data_output_;
@ -276,6 +277,7 @@ void AY38910::set_control_lines(ControlLines control_lines) {
}
void AY38910::update_bus() {
// Assume no output, unless this turns out to be a read.
data_output_ = 0xff;
switch(control_state_) {
default: break;

1
Components/AY38910/AY38910.hpp
View File

@ -94,7 +94,6 @@ class AY38910: public ::Outputs::Speaker::SampleSource {
int selected_register_ = 0;
uint8_t registers_[16] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
uint8_t output_registers_[16] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
uint8_t port_inputs_[2];
int master_divider_ = 0;