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Overture-CPU-Emulator
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Decode instructions using unions

This commit is contained in:
Curt Spark 2025-11-18 03:07:40 +00:00
parent b0f92beaed
commit a92eb11f4b
1 changed files with 23 additions and 25 deletions
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44
main.c
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@ -105,24 +105,19 @@ void overture_condition_jump(enum overture_condition_mode mode, uint8_t r0, uint
}; };
} }
typedef union overture_instruction {
typedef struct overture_decoded_instruction { uint8_t instruction;
uint8_t overture_mode : 2; union {
uint8_t left_operand : 3; struct {
uint8_t right_operand : 3;
uint8_t combined_immediate : 6; uint8_t combined_immediate : 6;
} overture_decoded_instruction; uint8_t overture_mode : 2;
overture_decoded_instruction overture_decode_instruction(uint8_t current_instruction) {
overture_decoded_instruction instruction = {
.overture_mode = current_instruction >> 6,
.left_operand = (current_instruction << 2) >> 5,
.right_operand = (current_instruction << 5) >> 5,
.combined_immediate = (current_instruction << 2) >> 2,
}; };
struct {
return instruction; uint8_t right_operand : 3;
uint8_t left_operand : 3;
}; };
};
} overture_instruction;
void overture_fetch_instruction(uint8_t program_counter, uint8_t* current_instruction, uint8_t rom[256]) { void overture_fetch_instruction(uint8_t program_counter, uint8_t* current_instruction, uint8_t rom[256]) {
*current_instruction = rom[program_counter - 1]; *current_instruction = rom[program_counter - 1];
@ -144,7 +139,7 @@ typedef struct overture {
uint8_t output; uint8_t output;
bool output_enable; bool output_enable;
uint8_t current_instruction; overture_instruction current_instruction;
} overture; } overture;
void sleep_hz(int hz) { void sleep_hz(int hz) {
@ -211,7 +206,7 @@ uint8_t* multiplex_destination(uint8_t operand, overture* cpu) {
return destination; return destination;
} }
void overture_execute_instruction(overture_decoded_instruction instruction, overture* cpu) { void overture_execute_instruction(overture_instruction instruction, overture* cpu) {
uint8_t* source_register = multiplex_source(instruction.left_operand, cpu); uint8_t* source_register = multiplex_source(instruction.left_operand, cpu);
uint8_t* destination_register = multiplex_destination(instruction.right_operand, cpu); uint8_t* destination_register = multiplex_destination(instruction.right_operand, cpu);
@ -252,9 +247,13 @@ void cpu_diagnostics(overture* cpu) {
printf("input: %d\n", cpu->input); printf("input: %d\n", cpu->input);
printf("output: %d\n", cpu->output); printf("output: %d\n", cpu->output);
printf("Output enabled?: %d\n", cpu->output_enable); printf("Output enabled?: %d\n\n", cpu->output_enable);
printf("Current instruction: %d\n\n", cpu->current_instruction); printf("Current instruction: %d\n", cpu->current_instruction.instruction);
printf("Mode: %d\n", cpu->current_instruction.overture_mode);
printf("Left Operand: %d\n", cpu->current_instruction.left_operand);
printf("Right Operand: %d\n", cpu->current_instruction.right_operand);
printf("Combined Immediate: %d\n\n", cpu->current_instruction.combined_immediate);
} }
void overture_cycle(overture* cpu, uint8_t rom[256]) { void overture_cycle(overture* cpu, uint8_t rom[256]) {
@ -263,10 +262,9 @@ void overture_cycle(overture* cpu, uint8_t rom[256]) {
}; };
cpu->program_counter += 1; cpu->program_counter += 1;
cpu->output_enable = false; cpu->output_enable = false;
overture_fetch_instruction(cpu->program_counter, &(cpu->current_instruction), rom); overture_fetch_instruction(cpu->program_counter, &(cpu->current_instruction.instruction), rom);
overture_decoded_instruction instruction = overture_decode_instruction(cpu->current_instruction); overture_execute_instruction(cpu->current_instruction, cpu);
overture_execute_instruction(instruction, cpu);
cpu_diagnostics(cpu); cpu_diagnostics(cpu);
} }
@ -301,7 +299,7 @@ int main() {
.output = 0, .output = 0,
.output_enable = true, .output_enable = true,
.current_instruction = 0 .current_instruction.instruction = 0
}; };
overture_start_clock(&cpu, rom); overture_start_clock(&cpu, rom);