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b5a470d3ba
When describing the CPU's reset pin, the W65C02S data sheet says: > All Registers are initialized by software except the Decimal and Interrupt > disable mode select bits of the Processor Status Register (P) are initialized > by hardware. It then has a diagram of the power-on state of the processor status register: > 7 6 5 4 3 2 1 0 > * * 1 1 0 1 * * > N V - B D I Z C > > * = software initialized Confusingly the text indicates that only the D and I flags are initialised by hardware, while the diagram indicates that the B flag is initialised too. Meanwhile, https://www.nesdev.org/wiki/CPU_power_up_state says that the power-on state of the NES CPU is $34 (exactly matching the diagram above) but https://www.nesdev.org/wiki/Status_flags#The_B_flag says that the B flag does not physically exist within P register, it's only relevant in the copy of P that gets pushed to the stack by BRK (set), PHP (set), or an interrupt signal (cleared). As a result, the most sensible power-on state for the processor status register is with the "interrupt disable" flag set and everything else cleared.
103 lines
3.2 KiB
Java
103 lines
3.2 KiB
Java
package com.loomcom.symon;
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import com.loomcom.symon.devices.Memory;
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import com.loomcom.symon.exceptions.MemoryAccessException;
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import junit.framework.TestCase;
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public class CpuIndirectModeTest extends TestCase {
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protected Cpu cpu;
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protected Bus bus;
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protected Memory mem;
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protected void setUp() throws Exception {
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this.cpu = new Cpu();
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this.bus = new Bus(0x0000, 0xffff);
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this.mem = new Memory(0x0000, 0xffff);
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bus.addCpu(cpu);
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bus.addDevice(mem);
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// Load the reset vector.
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bus.write(0xfffc, Bus.DEFAULT_LOAD_ADDRESS & 0x00ff);
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bus.write(0xfffd, (Bus.DEFAULT_LOAD_ADDRESS & 0xff00) >>> 8);
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cpu.reset();
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// Assert initial state
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assertEquals(0, cpu.getAccumulator());
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assertEquals(0, cpu.getXRegister());
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assertEquals(0, cpu.getYRegister());
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assertEquals(0x200, cpu.getProgramCounter());
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assertEquals(0xff, cpu.getStackPointer());
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assertEquals(0x24, cpu.getProcessorStatus());
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}
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/*
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* The following opcodes are tested for correctness in this file:
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*
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* JMP - $6c
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*
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*/
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/* JMP - Jump - $6c */
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public void test_JMP_notOnPageBoundary() throws MemoryAccessException {
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bus.write(0x3400, 0x00);
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bus.write(0x3401, 0x54);
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bus.loadProgram(0x6c, 0x00, 0x34);
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cpu.step();
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assertEquals(0x5400, cpu.getProgramCounter());
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// No change to status flags.
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assertEquals(0x24, cpu.getProcessorStatus());
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}
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public void test_JMP_with_ROR_Bug() throws MemoryAccessException {
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cpu.setBehavior(Cpu.CpuBehavior.NMOS_WITH_ROR_BUG);
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bus.write(0x3400, 0x22);
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bus.write(0x34ff, 0x00);
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bus.write(0x3500, 0x54);
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bus.loadProgram(0x6c, 0xff, 0x34);
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cpu.step();
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assertEquals(0x2200, cpu.getProgramCounter());
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// No change to status flags.
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assertEquals(0x24, cpu.getProcessorStatus());
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}
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public void test_JMP_withIndirectBug() throws MemoryAccessException {
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cpu.setBehavior(Cpu.CpuBehavior.NMOS_6502);
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bus.write(0x3400, 0x22);
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bus.write(0x34ff, 0x00);
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bus.write(0x3500, 0x54);
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bus.loadProgram(0x6c, 0xff, 0x34);
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cpu.step();
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assertEquals(0x2200, cpu.getProgramCounter());
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// No change to status flags.
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assertEquals(0x24, cpu.getProcessorStatus());
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}
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public void test_JMP_withOutIndirectBug() throws MemoryAccessException {
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cpu.setBehavior(Cpu.CpuBehavior.CMOS_6502);
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bus.write(0x3400, 0x22);
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bus.write(0x34ff, 0x00);
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bus.write(0x3500, 0x54);
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bus.loadProgram(0x6c, 0xff, 0x34);
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cpu.step();
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assertEquals(0x5400, cpu.getProgramCounter());
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// No change to status flags.
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assertEquals(0x24, cpu.getProcessorStatus());
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}
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public void test_JMP_cmos() throws MemoryAccessException {
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cpu.setBehavior(Cpu.CpuBehavior.CMOS_6502);
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bus.write(0x3400, 0x22);
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bus.write(0x34ff, 0x00);
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bus.write(0x3500, 0x54);
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bus.loadProgram(0x6c, 0xff, 0x34);
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cpu.step();
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assertEquals(0x5400, cpu.getProgramCounter());
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// No change to status flags.
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assertEquals(0x24, cpu.getProcessorStatus());
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}
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}
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