73 lines
2.1 KiB
C++
73 lines
2.1 KiB
C++
/*
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* File: Cpu6502Helper.cpp
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* Author: Christopher
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*
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* Created on December 12, 2013, 10:22 PM
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*/
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#include "Cpu6502Helper.h"
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#include "Cpu6502.h"
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#include "Common.h"
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#include "SegmentTypes.h"
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void Cpu6502Helper::powerOn() {
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PinSettings ps;
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// set voltage supply and ground.
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ps.insert(std::make_pair(this->common.VCC, true));
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ps.insert(std::make_pair(this->common.VSS, false));
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// don't do the set-overflow overriding functionality
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ps.insert(std::make_pair(this->common.SO, false));
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// ready to run (i.e., do not do single-stepping of instructions)
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ps.insert(std::make_pair(this->common.RDY, true));
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// pull up to indicate that we are not interrupting now
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ps.insert(std::make_pair(this->common.IRQ, true));
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ps.insert(std::make_pair(this->common.NMI, true));
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/*
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* RES_BAR pin means "not resetting". Since it is a negated pin, pulling it low means "resetting"
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* and pulling it high means "not resetting" or equivalently "running".
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*/
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/*
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* RES_BAR false: resetting now (i.e., in power-up now; pull high to begin normal operation)
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* We want to hold RES_BAR low for a while, indicating power-up phase during which the
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* CPU does not start up normal operations yet. The caller can set RES_BAR high (by calling
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* reset) whenever he is ready to start the CPU running.
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*/
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ps.insert(std::make_pair(this->common.RES, false));
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this->cpu.setPins(ps);
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this->nextPhase = true;
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}
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void Cpu6502Helper::tick() {
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step();
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step();
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}
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void Cpu6502Helper::step() {
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/*
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* We cheat a little bit here: instead of requiring the
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* caller to toggle clock-zero pin, we let him just call
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* "step" and *we* keep track of which phase we are in.
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* To do this, we just use the CLK0 segment value (as
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* a kind of temporary variable), and just toggle it in
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* order to know which phase we are going into.
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*
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* The real 6502, of course, does not do this.
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*/
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this->nextPhase = !this->nextPhase;
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this->cpu.clock(this->nextPhase);
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}
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void Cpu6502Helper::reset() {
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this->cpu.setPins(PinSettings{std::make_pair(this->common.RES, true)});
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}
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