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