From 5cea8025cebea28285c28566f7f4fa5cdcc5c131 Mon Sep 17 00:00:00 2001
From: Irmen de Jong <irmen@razorvine.net>
Date: Sat, 21 Sep 2019 23:16:55 +0200
Subject: [PATCH] Added irq() and nmi() to the MPU
---
CHANGES.txt | 4 ++++
py65/devices/mpu6502.py | 22 ++++++++++++++++++++
py65/tests/devices/test_mpu6502.py | 32 ++++++++++++++++++++++++++++++
3 files changed, 58 insertions(+)
diff --git a/CHANGES.txt b/CHANGES.txt
index b430d10..701bea8 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -9,6 +9,10 @@
Py65 now requires Python 3.4 or later. On Python 2, Py65 now requires
Python 2.7.
+ - added ``irq()`` and ``nmi()`` methods to the ``MPU`` class, so that
+ interrupts can be simulated. Patch by Irmen de Jong.
+
+
1.1.0 (2018-07-01)
------------------
diff --git a/py65/devices/mpu6502.py b/py65/devices/mpu6502.py
index 4166d70..b211570 100644
--- a/py65/devices/mpu6502.py
+++ b/py65/devices/mpu6502.py
@@ -74,6 +74,28 @@ class MPU:
self.p = self.BREAK | self.UNUSED
self.processorCycles = 0
+ def irq(self):
+ # triggers a normal IRQ
+ # this is very similar to the BRK instruction
+ if self.p & self.INTERRUPT:
+ return
+ self.stPushWord(self.pc)
+ self.p &= ~self.BREAK
+ self.stPush(self.p | self.UNUSED)
+ self.p |= self.INTERRUPT
+ self.pc = self.WordAt(self.IRQ)
+ self.processorCycles += 7
+
+ def nmi(self):
+ # triggers a NMI IRQ in the processor
+ # this is very similar to the BRK instruction
+ self.stPushWord(self.pc)
+ self.p &= ~self.BREAK
+ self.stPush(self.p | self.UNUSED)
+ self.p |= self.INTERRUPT
+ self.pc = self.WordAt(self.NMI)
+ self.processorCycles += 7
+
# Helpers for addressing modes
def ByteAt(self, addr):
diff --git a/py65/tests/devices/test_mpu6502.py b/py65/tests/devices/test_mpu6502.py
index 8cfd6a3..fc03a24 100644
--- a/py65/tests/devices/test_mpu6502.py
+++ b/py65/tests/devices/test_mpu6502.py
@@ -1905,6 +1905,38 @@ class Common6502Tests:
self.assertEqual(mpu.BREAK | mpu.UNUSED | mpu.INTERRUPT, mpu.p)
+ # IRQ and NMI handling (very similar to BRK)
+
+ def test_irq_pushes_pc_and_correct_status_then_sets_pc_to_irq_vector(self):
+ mpu = self._make_mpu()
+ mpu.p = mpu.UNUSED
+ self._write(mpu.memory, 0xFFFA, (0x88, 0x77))
+ self._write(mpu.memory, 0xFFFE, (0xCD, 0xAB))
+ mpu.pc = 0xC123
+ mpu.irq()
+ self.assertEqual(0xABCD, mpu.pc)
+ self.assertEqual(0xC1, mpu.memory[0x1FF]) # PCH
+ self.assertEqual(0x23, mpu.memory[0x1FE]) # PCL
+ self.assertEqual(mpu.UNUSED, mpu.memory[0x1FD]) # Status
+ self.assertEqual(0xFC, mpu.sp)
+ self.assertEqual(mpu.UNUSED | mpu.INTERRUPT, mpu.p)
+ self.assertEqual(7, mpu.processorCycles)
+
+ def test_nmi_pushes_pc_and_correct_status_then_sets_pc_to_nmi_vector(self):
+ mpu = self._make_mpu()
+ mpu.p = mpu.UNUSED
+ self._write(mpu.memory, 0xFFFA, (0x88, 0x77))
+ self._write(mpu.memory, 0xFFFE, (0xCD, 0xAB))
+ mpu.pc = 0xC123
+ mpu.nmi()
+ self.assertEqual(0x7788, mpu.pc)
+ self.assertEqual(0xC1, mpu.memory[0x1FF]) # PCH
+ self.assertEqual(0x23, mpu.memory[0x1FE]) # PCL
+ self.assertEqual(mpu.UNUSED, mpu.memory[0x1FD]) # Status
+ self.assertEqual(0xFC, mpu.sp)
+ self.assertEqual(mpu.UNUSED | mpu.INTERRUPT, mpu.p)
+ self.assertEqual(7, mpu.processorCycles)
+
# BVC
def test_bvc_overflow_clear_branches_relative_forward(self):