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Added stack functions.

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This commit is contained in:
Seth Morabito 2008-12-12 01:02:31 -08:00
parent 6915331cca
commit 7e36444193
2 changed files with 45 additions and 14 deletions
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30
src/main/java/com/loomcom/lm6502/Cpu.java
View File

@ -621,8 +621,11 @@ public class Cpu implements InstructionTable {
break;
}
}
public String statusString() {
/**
* Returns a string representing the CPU state.
*/
public String toString() {
String opcode = CpuUtils.opcode(ir, operands[0], operands[1]);
StringBuffer sb = new StringBuffer(String.format("$%04X", addr) + " ");
sb.append(String.format("%-12s", opcode));
@ -633,10 +636,31 @@ public class Cpu implements InstructionTable {
return sb.toString();
}
/**
* Push an item onto the stack, and decrement the stack counter.
* Silently fails to push onto the stack if SP is
* TODO: Unit tests.
*/
protected void push(int data) {
bus.write(sp, data);
if (sp > 0x100) { sp--; }
}
/**
* Pop a byte off the user stack, and increment the stack counter.
* TODO: Unit tests.
*/
protected int pop() {
int data = bus.read(sp);
if (sp < 0x1ff) { sp++; }
return data;
}
/*
* Increment the PC, rolling over if necessary.
*/
private void incProgramCounter() {
protected void incProgramCounter() {
if (pc == 0xffff) {
pc = 0;
} else {

29
src/main/java/com/loomcom/lm6502/Simulator.java
View File

@ -61,22 +61,29 @@ public class Simulator {
bus.write(0x0302, 0xea); // NOP
bus.write(0x0303, 0xea); // NOP
bus.write(0x0304, 0xea); // NOP
bus.write(0x0305, 0xea); // NOP
bus.write(0x0306, 0xa9); // LDA #$1A
bus.write(0x0307, 0x1a);
bus.write(0x0305, 0xa0); // LDY #$1A
bus.write(0x0306, 0x1a);
bus.write(0x0307, 0xea); // NOP
bus.write(0x0308, 0xea); // NOP
bus.write(0x0309, 0xea); // NOP
bus.write(0x030a, 0xa9); // LDA #$03
bus.write(0x030b, 0x03);
bus.write(0x030c, 0x4c); // JMP #$0300
bus.write(0x030d, 0x00);
bus.write(0x030e, 0x03);
bus.write(0x0309, 0xa2); // LDX #$03
bus.write(0x030a, 0x03);
bus.write(0x030b, 0xa9); // LDA #$00
bus.write(0x030c, 0x00);
bus.write(0x030d, 0xa2); // LDX #$00
bus.write(0x030e, 0x00);
bus.write(0x030f, 0xa0); // LDY #$00
bus.write(0x0310, 0x00);
bus.write(0x0311, 0x4c); // JMP #$0300
bus.write(0x0312, 0x00);
bus.write(0x0313, 0x03);
cpu.reset();
for (int i = 0; i < 60; i++) {
for (int i = 0; i <= 23; i++) {
cpu.step();
System.out.println(cpu.statusString());
System.out.println(cpu.toString());
}
}