mirror of https://github.com/jscrane/r65emu.git
60 lines
1.7 KiB
C++
60 lines
1.7 KiB
C++
#ifndef __PIA_H__
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#define __PIA_H__
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// Motorola 6820 / 6821 PIA
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// https://en.wikipedia.org/wiki/Peripheral_Interface_Adapter
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class PIA {
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public:
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PIA(): cra(0), ina(0), outa(0), ddra(0), crb(0), inb(0), outb(0), ddrb(0),
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ca1(false), ca2(false), irq_a1(false), irq_a2(false),
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cb1(false), cb2(false), irq_b1(false), irq_b2(false) {}
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virtual void reset() {
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outb = inb = crb = ddrb = outa = ina = cra = ddra = 0;
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irq_a1 = irq_a2 = irq_b1 = irq_b2 = ca1 = ca2 = cb1 = cb2 = false;
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}
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// device memory interface
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void write(Memory::address, uint8_t);
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uint8_t read(Memory::address);
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void checkpoint(Stream &);
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void restore(Stream &);
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// device input (external) interface
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void write_porta_in(uint8_t b) { ina = b; }
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void write_porta_in_bit(uint8_t, bool);
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void write_ca1(bool);
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void write_ca2(bool);
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void write_portb_in(uint8_t b) { inb = b; }
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void write_portb_in_bit(uint8_t, bool);
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void write_cb1(bool);
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void write_cb2(bool);
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static const uint8_t IRQ1 = 0x80;
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static const uint8_t IRQ2 = 0x40;
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protected:
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// overrideable device memory interface
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virtual uint8_t read_ddra() { return ddra; }
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virtual uint8_t read_porta();
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virtual uint8_t read_cra();
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virtual uint8_t read_ddrb() { return ddrb; }
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virtual uint8_t read_portb();
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virtual uint8_t read_crb();
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virtual void write_ddra(uint8_t b) { ddra = b; }
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virtual void write_porta(uint8_t b) { outa = b; }
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virtual void write_cra(uint8_t b) { cra = (b & 0x3f); }
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virtual void write_ddrb(uint8_t b) { ddrb = b; }
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virtual void write_portb(uint8_t b) { outb = b; }
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virtual void write_crb(uint8_t b) { crb = (b & 0x3f); }
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private:
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uint8_t cra, ina, outa, ddra;
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uint8_t crb, inb, outb, ddrb;
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bool ca1, ca2, irq_a1, irq_a2;
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bool cb1, cb2, irq_b1, irq_b2;
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};
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#endif
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