EightBit/src/Processor.cpp

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#include "stdafx.h"
#include "Processor.h"
EightBit::Processor::Processor(Bus& bus)
: m_bus(bus) {
}
void EightBit::Processor::powerOn() {
Chip::powerOn();
raise(RESET());
raise(HALT());
raise(INT());
}
void EightBit::Processor::handleRESET() {
raise(RESET());
PC() = 0;
}
void EightBit::Processor::handleINT() {
raise(INT());
}
void EightBit::Processor::handleIRQ() {
raise(IRQ());
}
int EightBit::Processor::run(const int limit) {
int current = 0;
while (LIKELY(powered() && (current < limit)))
current += step();
return current;
}
// http://graphics.stanford.edu/~seander/bithacks.html#FixedSignExtend
int8_t EightBit::Processor::signExtend(const int b, uint8_t x) {
const uint8_t m = 1 << (b - 1); // mask can be pre-computed if b is fixed
x = x & ((1 << b) - 1); // (Skip this if bits in x above position b are already zero.)
const auto result = (x ^ m) - m;
return result;
}
void EightBit::Processor::ret() {
jump(popWord());
}