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r65emu/pia.cpp
2023-09-30 13:37:08 +01:00

194 lines
3.4 KiB
C++

#include <Arduino.h>
#include <memory.h>
#include "pia.h"
// see: https://github.com/mamedev/mame/blob/master/src/devices/machine/6821pia.cpp
// and: https://github.com/mamedev/mame/blob/master/src/devices/machine/6821pia.h
inline bool c1_low_to_high(uint8_t cr) { return cr & 0x02; }
inline bool c1_high_to_low(uint8_t cr) { return !c1_low_to_high(cr); }
inline bool c2_output(uint8_t cr) { return cr & 0x20; }
inline bool c2_input(uint8_t cr) { return !c2_input(cr); }
inline bool c2_low_to_high(uint8_t cr) { return cr & 0x10; }
inline bool c2_high_to_low(uint8_t cr) { return !c2_low_to_high(cr); }
inline bool output_selected(uint8_t cr) { return cr & 0x04; }
void PIA::write(Memory::address a, uint8_t b) {
#if defined(DEBUGGING)
Serial.print(millis());
Serial.print(" > ");
Serial.print(a, 16);
Serial.print(' ');
Serial.println(b, 16);
#endif
switch(a & 3) {
case 0:
output_selected(cra)? write_porta(b): write_ddra(b);
break;
case 1:
write_cra(b);
break;
case 2:
output_selected(crb)? write_portb(b): write_ddrb(b);
break;
case 3:
write_crb(b);
break;
}
}
uint8_t PIA::read(Memory::address a) {
#if defined(DEBUGGING)
Serial.print(millis());
Serial.print(" < ");
Serial.println(a, 16);
#endif
switch (a & 3) {
case 0:
return output_selected(cra)? read_porta(): read_ddra();
case 1:
return read_cra();
case 2:
return output_selected(crb)? read_portb(): read_ddrb();
case 3:
return read_crb();
}
return 0xff;
}
void PIA::checkpoint(Stream &s) {
s.write(crb);
s.write(outb);
s.write(inb);
s.write(ddrb);
s.write(cra);
s.write(outa);
s.write(ina);
s.write(ddra);
s.write(irq_b1);
s.write(irq_b2);
s.write(irq_a1);
s.write(irq_a2);
s.write(cb1);
s.write(cb2);
s.write(ca1);
s.write(ca2);
}
void PIA::restore(Stream &s) {
crb = s.read();
outb = s.read();
inb = s.read();
ddrb = s.read();
cra = s.read();
outa = s.read();
ina = s.read();
ddra = s.read();
irq_b1 = s.read();
irq_b2 = s.read();
irq_a1 = s.read();
irq_a2 = s.read();
cb1 = s.read();
cb2 = s.read();
ca1 = s.read();
ca2 = s.read();
}
void PIA::write_ca1(bool state) {
if (ca1 == state)
return;
if ((state && c1_low_to_high(cra)) || (!state && c1_high_to_low(cra)))
irq_a1 = true;
ca1 = state;
}
void PIA::write_ca2(bool state) {
if (ca2 == state || !c2_input(cra))
return;
if ((state && c2_low_to_high(cra)) || (!state && c2_high_to_low(cra)))
irq_a2 = true;
ca2 = state;
}
void PIA::write_cb1(bool state) {
if (cb1 == state)
return;
if ((state && c1_low_to_high(crb)) || (!state && c1_high_to_low(crb)))
irq_b1 = true;
cb1 = state;
}
void PIA::write_cb2(bool state) {
if (cb2 == state || !c2_input(crb))
return;
if ((state && c2_low_to_high(crb)) || (!state && c2_high_to_low(crb)))
irq_b2 = true;
cb2 = state;
}
uint8_t PIA::read_cra() {
uint8_t b = cra;
if (irq_a1)
b |= IRQ1;
if (irq_a2 && c2_input(cra))
b |= IRQ2;
return b;
}
uint8_t PIA::read_crb() {
uint8_t b = crb;
if (irq_b1)
b |= IRQ1;
if (irq_b2 && c2_input(crb))
b |= IRQ2;
return b;
}
uint8_t PIA::read_porta() {
irq_a1 = irq_a2 = false;
return (ina & ~ddra) | (outa & ddra);
}
uint8_t PIA::read_portb() {
irq_b1 = irq_b2 = false;
return (inb & ~ddrb) | (outb & ddrb);
}
void PIA::write_porta_in_bit(uint8_t mask, bool state) {
if (state)
ina |= mask;
else
ina &= ~mask;
}
void PIA::write_portb_in_bit(uint8_t mask, bool state) {
if (state)
inb |= mask;
else
inb &= ~mask;
}