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Computer-Architecture - Scott Bren #203

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b534a9e
initial commit
smbren Mar 4, 2019
d6d31d4
working on cpu_init() method
smbren Mar 4, 2019
af2e45e
cpu_init initializes PC, registers, and ram to 0
smbren Mar 4, 2019
09ee131
working on cpu_run
smbren Mar 4, 2019
1775f6f
fixed cpu_run
smbren Mar 5, 2019
39c12cd
working on reading from files
smbren Mar 5, 2019
2209395
added MUL instruction
smbren Mar 5, 2019
b166ef5
working on reading from a file
smbren Mar 5, 2019
93b85a6
working on reading from a file
smbren Mar 5, 2019
44eed72
fixed loading instructions from ls8 files
smbren Mar 6, 2019
e0a7c49
working on system stack
smbren Mar 6, 2019
49922c4
system stack added, stack.ls8 runs
smbren Mar 6, 2019
b571fe1
fixed a bug in system stack
smbren Mar 6, 2019
0937a08
working on CALL and RET instructions
smbren Mar 7, 2019
751d167
working on CALL instruction
smbren Mar 7, 2019
21938c4
all tests pass MVP complete
smbren Mar 8, 2019
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9 changes: 6 additions & 3 deletions ls8/cpu.c
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Original file line number Diff line number Diff line change
Expand Up @@ -126,13 +126,16 @@ void cpu_run(struct cpu *cpu)
case CALL:
sp--;
stack[sp] = cpu->registers[operandA];
cpu->PC = operandA;
stack[operandA];
cpu->PC = cpu->registers[operandA];

cpu_ram_read(cpu, cpu->PC);
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@Tulf Tulf Mar 7, 2019

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Should be writing to RAM instead:
cpu_ram_write(cpu, stack[sp], cpu->pc+2);
But the way you setup your stack will conlfict with this. It may be easier for you to just create push and pop functions to increment and derement the stack pointer and then write the value you want to push to ram at the stack pointer.
Something like this:
push (struct *cpu, unsigned char val): { cpu->registers[sp] --; cpu_ram_write(cpu, val, cpu->reg[sp]); }

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@Tulf Tulf Mar 7, 2019

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So with what you're doing I think you're just reading from RAM at the program count, and never even referencing the stack.

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@Tulf Tulf Mar 7, 2019

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Not entirely sure how you can call the right instruction this way.

break;

case RET:
cpu->PC = stack[sp];
cpu->registers[operandA] = stack[sp];
sp++;

cpu->PC = cpu->registers[operandA];
break;


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