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r65emu/pia.h
2023-11-15 18:22:28 +00:00

60 lines
1.7 KiB
C++

#ifndef __PIA_H__
#define __PIA_H__
// Motorola 6820 / 6821 PIA
// https://en.wikipedia.org/wiki/Peripheral_Interface_Adapter
class PIA {
public:
PIA(): cra(0), ina(0), outa(0), ddra(0), crb(0), inb(0), outb(0), ddrb(0),
ca1(false), ca2(false), irq_a1(false), irq_a2(false),
cb1(false), cb2(false), irq_b1(false), irq_b2(false) {}
virtual void reset() {
outb = inb = crb = ddrb = outa = ina = cra = ddra = 0;
irq_a1 = irq_a2 = irq_b1 = irq_b2 = ca1 = ca2 = cb1 = cb2 = false;
}
// device memory interface
void write(Memory::address, uint8_t);
uint8_t read(Memory::address);
void checkpoint(Stream &);
void restore(Stream &);
// device input (external) interface
void write_porta_in(uint8_t b) { ina = b; }
void write_porta_in_bit(uint8_t, bool);
void write_ca1(bool);
void write_ca2(bool);
void write_portb_in(uint8_t b) { inb = b; }
void write_portb_in_bit(uint8_t, bool);
void write_cb1(bool);
void write_cb2(bool);
static const uint8_t IRQ1 = 0x80;
static const uint8_t IRQ2 = 0x40;
protected:
// overrideable device memory interface
virtual uint8_t read_ddra() { return ddra; }
virtual uint8_t read_porta();
virtual uint8_t read_cra();
virtual uint8_t read_ddrb() { return ddrb; }
virtual uint8_t read_portb();
virtual uint8_t read_crb();
virtual void write_ddra(uint8_t b) { ddra = b; }
virtual void write_porta(uint8_t b) { outa = b; }
virtual void write_cra(uint8_t b) { cra = (b & 0x3f); }
virtual void write_ddrb(uint8_t b) { ddrb = b; }
virtual void write_portb(uint8_t b) { outb = b; }
virtual void write_crb(uint8_t b) { crb = (b & 0x3f); }
private:
uint8_t cra, ina, outa, ddra;
uint8_t crb, inb, outb, ddrb;
bool ca1, ca2, irq_a1, irq_a2;
bool cb1, cb2, irq_b1, irq_b2;
};
#endif