Apple1-esp/pia.h
Stephen Crane db9de4bdde update
2018-08-14 11:00:03 +01:00

52 lines
1.1 KiB
C++

#ifndef __PIA_H__
#define __PIA_H__
class pia: public Memory::Device {
public:
pia(): Memory::Device(256), portb_cr(0), porta_cr(0) {}
virtual void reset() { portb_cr = porta_cr = 0; }
void operator=(uint8_t);
operator uint8_t();
void checkpoint(Stream &);
void restore(Stream &);
protected:
// write to the "external" side of the port
void set_porta(uint8_t b) {
porta = b;
if (b & 0x80)
porta_cr = 0xa7;
}
// "device-side" operations (called from memory interface)
uint8_t read_porta() { return porta; }
virtual uint8_t read_porta_cr() {
if (porta_cr & 0x80) {
porta_cr = 0;
return 0xa7;
}
return porta_cr;
}
uint8_t read_portb() { return portb; }
uint8_t read_portb_cr() { return portb_cr; }
void write_porta(uint8_t b) { porta = b; }
void write_porta_cr(uint8_t b) {
if (!(porta_cr & 0x80) && b >= 0x80)
porta_cr |= 0x80;
else
porta_cr = b;
}
virtual void write_portb(uint8_t b) { portb = b; }
void write_portb_cr(uint8_t b) {
if (portb_cr < 0x80)
portb_cr = b;
}
private:
uint8_t portb_cr, portb, porta_cr, porta;
};
#endif