jake/SplitBit-Emulator
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Added bit shift instructions.

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SHL and SHR treat A and B as a 16 bit circular shift register and rotates them either left or right.
This commit is contained in:
Anachronaut
2024-10-30 16:06:33 -04:00
committed by GitHub
parent a58fb3d694
commit c64f097810
3 changed files with 21 additions and 1 deletions
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Source/Emulator/cpu.c
+16
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@@ -6,6 +6,8 @@
#include "cpu.h"
#include "io.h"
uint16_t shiftRegister;
void initializeCPU(CPURegisters *cpu, uint8_t *programMemory, uint8_t *dataMemory) {
cpu->A = 0;
cpu->B = 0;
@@ -80,6 +82,20 @@ uint8_t executeOperation(uint8_t Instruction, CPURegisters *cpu) {
// NOTB - not B -> Q
cpu->Q = ~cpu->B;
break;
case 0x09:
// SHL - Shift AB left.
shiftRegister = ((uint16_t)cpu->A << 8) | cpu->B;
shiftRegister = (shiftRegister << 1) | (shiftRegister >> 15);
cpu->A = shiftRegister >> 8;
cpu->B = shiftRegister & 0xFF;
break;
case 0x0A:
// SHR - Shift AB right.
shiftRegister = ((uint16_t)cpu->A << 8) | cpu->B;
shiftRegister = (shiftRegister >> 1) | (shiftRegister << 15);
cpu->A = shiftRegister >> 8;
cpu->B = shiftRegister & 0xFF;
break;
//
// 1x - Branch Operations:
//