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Begins trying to receive ACIA data.

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This commit is contained in:
Thomas Harte 2019-10-21 20:10:19 -04:00
parent cf37e9f5de
commit 83f5f0e2ad
2 changed files with 42 additions and 19 deletions
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50
Components/6850/6850.cpp
View File

@ -30,8 +30,8 @@ uint8_t ACIA::read(int address) {
} else {
LOG("Read status");
return
((received_data_ == NoValue) ? 0x00 : 0x01) |
((next_transmission_ == NoValue) ? 0x02 : 0x00) |
((received_data_ & NoValueMask) ? 0x00 : 0x01) |
((next_transmission_ == NoValueMask) ? 0x02 : 0x00) |
(data_carrier_detect.read() ? 0x04 : 0x00) |
(clear_to_send.read() ? 0x08 : 0x00) |
(interrupt_request_ ? 0x80 : 0x00)
@ -106,7 +106,7 @@ void ACIA::run_for(HalfCycles length) {
// rather than a 'while' is correct here. It's the responsibilit of the caller
// to ensure run_for lengths are appropriate for longer sequences.
if(transmit_advance >= write_data_time_remaining) {
if(next_transmission_ != NoValue) {
if(next_transmission_ != NoValueMask) {
transmit.advance_writer(write_data_time_remaining);
consider_transmission();
transmit.advance_writer(transmit_advance - write_data_time_remaining);
@ -124,7 +124,7 @@ void ACIA::run_for(HalfCycles length) {
}
void ACIA::consider_transmission() {
if(next_transmission_ != NoValue && !transmit.write_data_time_remaining()) {
if(next_transmission_ != NoValueMask && !transmit.write_data_time_remaining()) {
// Establish start bit and [7 or 8] data bits.
if(data_bits_ == 7) next_transmission_ &= 0x7f;
int transmission = next_transmission_ << 1;
@ -132,13 +132,7 @@ void ACIA::consider_transmission() {
// Add a parity bit, if any.
int mask = 0x2 << data_bits_;
if(parity_ != Parity::None) {
next_transmission_ ^= next_transmission_ >> 4;
next_transmission_ ^= next_transmission_ >> 2;
next_transmission_ ^= next_transmission_ >> 1;
if((next_transmission_&1) != (parity_ == Parity::Even)) {
transmission |= mask;
}
transmission |= parity(uint8_t(next_transmission_)) ? mask : 0;
mask <<= 1;
}
@ -149,7 +143,7 @@ void ACIA::consider_transmission() {
}
// Output all that.
const int total_bits = 1 + data_bits_ + stop_bits_ + (parity_ != Parity::None);
const int total_bits = expected_bits();
if(!next_transmission_) {
printf("");
}
@ -157,7 +151,7 @@ void ACIA::consider_transmission() {
printf("Transmitted %02x [%03x]\n", next_transmission_, transmission);
// Mark the transmit register as empty again.
next_transmission_ = NoValue;
next_transmission_ = NoValueMask;
}
}
@ -176,7 +170,31 @@ bool ACIA::get_interrupt_line() const {
return interrupt_request_;
}
bool ACIA::serial_line_did_produce_bit(Serial::Line *line, int bit) {
// TODO: how does this affect signalling?
return false;
int ACIA::expected_bits() {
return 1 + data_bits_ + stop_bits_ + (parity_ != Parity::None);
}
uint8_t ACIA::parity(uint8_t value) {
value ^= value >> 4;
value ^= value >> 2;
value ^= value >> 1;
return value ^ (parity_ == Parity::Even);
}
bool ACIA::serial_line_did_produce_bit(Serial::Line *line, int bit) {
// Shift this bit into the 11-bit input register; this is big enough to hold
// the largest transmission symbol.
++bits_received_;
bits_incoming_ = (bits_incoming_ >> 1) | (bit << 11);
printf("i: %d\n", bit);
// If that's the now-expected number of bits, update.
const int bit_target = expected_bits();
if(bits_received_ == bit_target) {
received_data_ = uint8_t(bits_incoming_ >> (12 - bit_target));
printf("r: %02x\n", received_data_);
return false;
}
return true;
}

11
Components/6850/6850.hpp
View File

@ -72,11 +72,16 @@ class ACIA: public ClockingHint::Source, private Serial::Line::ReadDelegate {
} parity_ = Parity::None;
int data_bits_ = 7, stop_bits_ = 2;
static const int NoValue = 0x100;
int next_transmission_ = NoValue;
int received_data_ = NoValue;
static const int NoValueMask = 0x100;
int next_transmission_ = NoValueMask;
int received_data_ = NoValueMask;
int bits_received_ = 0;
int bits_incoming_ = 0;
void consider_transmission();
int expected_bits();
uint8_t parity(uint8_t value);
bool receive_interrupt_enabled_ = false;
bool transmit_interrupt_enabled_ = false;