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245 lines
8.6 KiB
Swift
245 lines
8.6 KiB
Swift
//
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// Z80InterruptTests.swift
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// Clock Signal
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//
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// Created by Thomas Harte on 03/06/2017.
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// Copyright 2017 Thomas Harte. All rights reserved.
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//
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import XCTest
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class Z80InterruptTests: XCTestCase {
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private func assertNMI(machine: CSTestMachineZ80) {
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// confirm that the PC is now at 0x66, that the old is on the stack and
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// that IFF1 has migrated to IFF2
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XCTAssertEqual(machine.value(for: .programCounter), 0x66)
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XCTAssertEqual(machine.value(atAddress: 0xffff), 0x01)
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XCTAssertEqual(machine.value(atAddress: 0xfffe), 0x02)
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XCTAssertEqual(machine.value(for: .IFF2), 0)
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}
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func testNMI() {
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// Per http://www.z80.info/interrup.htm NMI should take 11 cycles to get to 0x66:
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// M1 cycle: 5 T states to do an opcode read and decrement SP
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// M2 cycle: 3 T states write high byte of PC to the stack and decrement SP
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// M3 cycle: 3 T states write the low byte of PC and jump to #0066.
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let machine = CSTestMachineZ80()
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// start the PC at 0x0100 and install two NOPs for it
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machine.setValue(0x0100, for: .programCounter)
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machine.setValue(0, for: .IFF1)
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machine.setValue(1, for: .IFF2)
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machine.setValue(0x00, atAddress: 0x0100)
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machine.setValue(0x00, atAddress: 0x0101)
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// put the stack at the top of memory
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machine.setValue(0, for: .stackPointer)
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// run for four cycles, and signal an NMI
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machine.runForNumber(ofCycles: 4)
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machine.nmiLine = true
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// run for four more cycles to get to where the NMI should be recognised
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machine.runForNumber(ofCycles: 4)
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XCTAssertEqual(machine.value(for: .programCounter), 0x0102)
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// run for eleven more cycles to allow the NMI to begin
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machine.runForNumber(ofCycles: 11)
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assertNMI(machine: machine)
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}
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func testHaltNMIWait() {
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let machine = CSTestMachineZ80()
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// start the PC at 0x0100 and install a NOP and a HALT for it
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machine.setValue(0x0100, for: .programCounter)
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machine.setValue(0, for: .IFF1)
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machine.setValue(1, for: .IFF2)
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machine.setValue(0x00, atAddress: 0x0100)
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machine.setValue(0x76, atAddress: 0x0101)
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// put the stack at the top of memory
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machine.setValue(0, for: .stackPointer)
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// run for ten cycles, check that the processor is halted and assert an NMI
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machine.runForNumber(ofCycles: 10)
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XCTAssert(machine.isHalted, "Machine should be halted")
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machine.nmiLine = true
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// check that the machine ceases believing itsef to be halted after two cycles
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machine.runForNumber(ofCycles: 1)
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XCTAssert(machine.isHalted, "Machine should still be halted")
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machine.runForNumber(ofCycles: 1)
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XCTAssert(!machine.isHalted, "Machine should no longer be halted")
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// assert wait
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machine.waitLine = true
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// run for twenty cycles, an arbitrary big number
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machine.runForNumber(ofCycles: 20)
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// release wait
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machine.waitLine = false
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// NMI should have run for two cycles, then waited, so now there should be nine cycles left
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machine.runForNumber(ofCycles: 9)
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assertNMI(machine: machine)
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}
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func testIRQDisabled() {
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let machine = CSTestMachineZ80()
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// start the PC at 0x0100, interrupts disabled
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machine.setValue(0x0100, for: .programCounter)
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machine.setValue(0, for: .IFF1)
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machine.setValue(0, for: .IFF2)
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// install six NOPs
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for address: UInt16 in 0x0100 ..< 0x0106 {
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machine.setValue(0x00, atAddress: address)
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}
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// replace the fourth NOP with an EI
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machine.setValue(0xfb, atAddress: 0x0103)
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// run for four cycles, signal IRQ and run for 8 more
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machine.runForNumber(ofCycles: 4)
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machine.irqLine = true
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machine.runForNumber(ofCycles: 8)
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// confirm that the request was ignored
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XCTAssertEqual(machine.value(for: .programCounter), 0x0103)
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// run for 12 more cycles, hitting the EI and, if no interrupt occured, the two NOPs after it
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machine.runForNumber(ofCycles: 12)
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// confirm that an interruption occurred, causing the PC not yet to have proceeded beyond 0x0105
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XCTAssertEqual(machine.value(for: .programCounter), 0x0105)
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}
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func testIRQMode0() {
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// In interrupt mode 0, receipt of an IRQ causes an instruction to be read from the bus and
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// executed, with a two-cycle penalty. The test machine posts 0x21 during an interrupt acknowledge
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// cycle so the instruction that is executed will be LD HL, nnnn
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let machine = CSTestMachineZ80()
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// start the PC at 0x0100 and install two NOPs for it and then one copy of 0x83, then
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// something that isn't 0x83, and ensuring interrupts are enabled and in mode 1
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machine.setValue(0x0100, for: .programCounter)
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machine.setValue(1, for: .IFF1)
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machine.setValue(0, for: .IM)
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machine.setValue(0x1010, for: .HL)
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machine.setValue(0x00, atAddress: 0x0100)
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machine.setValue(0x00, atAddress: 0x0101)
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machine.setValue(0x83, atAddress: 0x0102)
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machine.setValue(0x9b, atAddress: 0x0103)
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// run for four cycles, and signal an IRQ
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machine.runForNumber(ofCycles: 4)
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machine.irqLine = true
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// run for four more cycles to get to where the IRQ should be recognised
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machine.runForNumber(ofCycles: 4)
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XCTAssertEqual(machine.value(for: .programCounter), 0x0102)
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// run for twelve more cycles, to complete a LD HL, nnnn with the additional two cycles
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// of cost for it being an IRQ program
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machine.runForNumber(ofCycles: 12)
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// confirm that the PC is still where it was, but HL is now 0x8383, and interrupts are disabled
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XCTAssertEqual(machine.value(for: .programCounter), 0x0102)
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XCTAssertEqual(machine.value(for: .HL), 0x8383)
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XCTAssertEqual(machine.value(for: .IFF1), 0)
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}
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func testIRQMode1() {
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// In interrupt mode 1, receipt of an IRQ means that the interrupt flag is disabled,
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// the PC is pushed to the stack and execution resumes at 0x38. This should take
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// 13 cycles total, per http://www.z80.info/interrup.htm
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let machine = CSTestMachineZ80()
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// start the PC at 0x0100 and install three NOPs for it, ensuring interrupts are enabled
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// and in mode 1
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machine.setValue(0x0100, for: .programCounter)
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machine.setValue(1, for: .IFF1)
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machine.setValue(1, for: .IM)
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machine.setValue(0x00, atAddress: 0x0100)
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machine.setValue(0x00, atAddress: 0x0101)
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machine.setValue(0x00, atAddress: 0x0102)
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// put the stack at the top of memory
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machine.setValue(0, for: .stackPointer)
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// run for four cycles, and signal an IRQ
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machine.runForNumber(ofCycles: 4)
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machine.irqLine = true
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// run for four more cycles to get to where the IRQ should be recognised
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machine.runForNumber(ofCycles: 4)
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XCTAssertEqual(machine.value(for: .programCounter), 0x0102)
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// run for twelve cycles and confirm that the IRQ has yet to begin
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machine.runForNumber(ofCycles: 12)
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XCTAssertNotEqual(machine.value(for: .programCounter), 0x38)
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// run for one more cycles to allow the IRQ to begin
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machine.runForNumber(ofCycles: 1)
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// confirm that the PC is now at 0x38, that the old is on the stack and
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// that interrupts are now disabled
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XCTAssertEqual(machine.value(for: .programCounter), 0x38)
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XCTAssertEqual(machine.value(atAddress: 0xffff), 0x01)
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XCTAssertEqual(machine.value(atAddress: 0xfffe), 0x02)
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XCTAssertEqual(machine.value(for: .IFF1), 0)
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}
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func testIRQMode2() {
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// In interrupt mode 2, the current bus value is combined with the I register to look
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// up a vector from memory; the PC calls that vector. Total cost: 19 cycles.
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let machine = CSTestMachineZ80()
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// start the PC at 0x0100 and install two NOPs for it and then one copy of 0x83, then
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// something that isn't 0x83, and ensuring interrupts are enabled and in mode 1
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machine.setValue(0x0100, for: .programCounter)
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machine.setValue(1, for: .IFF1)
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machine.setValue(2, for: .IM)
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machine.setValue(0x00, atAddress: 0x0100)
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machine.setValue(0x00, atAddress: 0x0101)
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// set I to 0x0200 to establish the location of our vector table, and because the test
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// machine will post a 0x21 in response to the interrupt cycle, at 0x0221 put the
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// arbitrarily-chosen address 0x8049
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machine.setValue(0x02, for: .I)
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machine.setValue(0x49, atAddress: 0x0221)
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machine.setValue(0x80, atAddress: 0x0222)
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// put the stack at the top of memory
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machine.setValue(0, for: .stackPointer)
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// run for four cycles, and signal an IRQ
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machine.runForNumber(ofCycles: 4)
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machine.irqLine = true
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// run for four more cycles to get to where the IRQ should be recognised
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machine.runForNumber(ofCycles: 4)
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XCTAssertEqual(machine.value(for: .programCounter), 0x0102)
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// run for nineteen more cycles, to complete the interrupt beginning
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machine.runForNumber(ofCycles: 19)
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// confirm that the PC is now at 0x8049, the old is on the stack, and interrupts
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// are disabled
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XCTAssertEqual(machine.value(for: .programCounter), 0x8049)
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XCTAssertEqual(machine.value(atAddress: 0xffff), 0x01)
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XCTAssertEqual(machine.value(atAddress: 0xfffe), 0x02)
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XCTAssertEqual(machine.value(for: .IFF1), 0)
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}
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}
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