prodriguez/choco-chip8
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Implemented most FXXX instructions.

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It now passes the Corax+ test.
This commit is contained in:
Pablo Rodriguez
2024-11-29 18:44:31 -05:00
parent ea4b961d53
commit 830ab9eda7
2 changed files with 70 additions and 31 deletions
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52
Interpreter.cpp
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@@ -4,6 +4,7 @@
namespace chocochip8 {
// converts any 8-bit sprite row to its high-res 16-bit equivalent
constexpr uint16_t gcvLowResToHighResRowLookupTable[256] = {
0x0000, 0x0003, 0x000C, 0x000F, 0x0030, 0x0033, 0x003C, 0x003F, 0x00C0, 0x00C3, 0x00CC, 0x00CF, 0x00F0, 0x00F3, 0x00FC, 0x00FF,
0x0300, 0x0303, 0x030C, 0x030F, 0x0330, 0x0333, 0x033C, 0x033F, 0x03C0, 0x03C3, 0x03CC, 0x03CF, 0x03F0, 0x03F3, 0x03FC, 0x03FF,
@@ -23,6 +24,7 @@ constexpr uint16_t gcvLowResToHighResRowLookupTable[256] = {
0xFF00, 0xFF03, 0xFF0C, 0xFF0F, 0xFF30, 0xFF33, 0xFF3C, 0xFF3F, 0xFFC0, 0xFFC3, 0xFFCC, 0xFFCF, 0xFFF0, 0xFFF3, 0xFFFC, 0xFFFF
};
// 4x5 sprites for hex digits 0-F
constexpr uint8_t gcvLowResFontData[80] = {
0xF0, 0x90, 0x90, 0x90, 0xF0,
0x20, 0x60, 0x20, 0x20, 0x70,
@@ -68,8 +70,11 @@ void Interpreter::tick() {
};
// fetch instruction
sreg_t pc = mvSpecialReg[SR_PC];
unsigned inst = (mvMemory[pc] << 8) | mvMemory[pc + 1];
sreg_t iInstAddr = mvSpecialReg[SR_PC];
unsigned inst = (mvMemory[iInstAddr] << 8) | mvMemory[iInstAddr + 1];
// increment program counter
mvSpecialReg[SR_PC] += 2;
// extract fields
unsigned iRegDst = (inst & 0x0F00) >> 8; // destination register index
@@ -99,7 +104,7 @@ void Interpreter::tick() {
mvSpecialReg[SR_PC] = imm12;
break;
case 0x2000: // 2NNN - call subroutine
mCallStack.push(pc);
mCallStack.push(mvSpecialReg[SR_PC]);
mvSpecialReg[SR_PC] = imm12;
break;
case 0x3000: // 3XNN - skip if equal immediate
@@ -138,12 +143,47 @@ void Interpreter::tick() {
case 0xE000: // EX9E, EXA1 - keypad access
break;
case 0xF000: // several unique instructions
switch(inst & 0xF0FF) {
case 0xF007: // FX07 - read timer register
mvReg[iRegDst] = (mvSpecialReg[SR_T1] + mcTicksPerSecond - 1) / mcTicksPerSecond;
break;
case 0xF015: // FX15 - set timer register
mvSpecialReg[SR_T1] = mcTicksPerSecond * mvReg[iRegDst];
break;
case 0xF018: // FX18 - set sound timer register
if(mvSpecialReg[SR_T1] == 0 && mvReg[iRegDst] != 0) {
mrBuzzer.on();
}
mvSpecialReg[SR_T1] = mcTicksPerSecond * mvReg[iRegDst];
break;
case 0xF01E: // FX1E - add to I
mvSpecialReg[SR_I] += mvReg[iRegDst];
break;
case 0xF029: // FX29 - set I to address of font sprite data for digit X
mvSpecialReg[SR_I] = scLowRestFontAddr + 5 * mvReg[iRegDst];
break;
case 0xF033: // FX33 - convert to bcd
mvMemory[mvSpecialReg[SR_I]] = (mvReg[iRegDst] / 100) % 10;
mvMemory[mvSpecialReg[SR_I] + 1] = (mvReg[iRegDst] / 10) % 10;
mvMemory[mvSpecialReg[SR_I] + 2] = mvReg[iRegDst] % 10;
break;
case 0xF055: // FX55 - dump registers
for(int i = 0; i <= iRegDst - R_V0; i++) {
mvMemory[mvSpecialReg[SR_I]++] = mvReg[R_V0 + i];
}
break;
case 0xF065: // FX65 - restore registers
for(int i = 0; i <= iRegDst - R_V0; i++) {
mvReg[R_V0 + i] = mvMemory[mvSpecialReg[SR_I]++];
}
break;
default:
throw std::invalid_argument("not implemented");
break;
}
break;
}
// increment PC
mvSpecialReg[SR_PC] += 2;
// decrement timers
if(mvSpecialReg[SR_T1] > 0) {
mvSpecialReg[SR_T1] -= 1;