From eb761bc62f176ec3eb012660c4a640a34b57fee0 Mon Sep 17 00:00:00 2001
From: Adrian Conlon <adrian.conlon@gmail.com>
Date: Fri, 13 Nov 2020 14:50:12 +0000
Subject: [PATCH] LR35902: Whoops: correct broken timer (when it begins at
 zero!)

Signed-off-by: Adrian Conlon <adrian.conlon@gmail.com>
---
 LR35902/src/IoRegisters.cpp | 2 +-
 LR35902/src/LR35902.cpp     | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/LR35902/src/IoRegisters.cpp b/LR35902/src/IoRegisters.cpp
index 47bded6..a86ba4e 100644
--- a/LR35902/src/IoRegisters.cpp
+++ b/LR35902/src/IoRegisters.cpp
@@ -153,7 +153,7 @@ void EightBit::GameBoy::IoRegisters::incrementTimers() {
 
 void EightBit::GameBoy::IoRegisters::incrementTimer() {
 	if (timerEnabled()) {
-		if (--m_timerCounter == 0) {
+		if (--m_timerCounter <= 0) {
 			m_timerCounter += m_timerRate;
 			incrementTIMA();
 		}
diff --git a/LR35902/src/LR35902.cpp b/LR35902/src/LR35902.cpp
index 81ee835..2b10635 100644
--- a/LR35902/src/LR35902.cpp
+++ b/LR35902/src/LR35902.cpp
@@ -340,6 +340,7 @@ int EightBit::GameBoy::LR35902::step() {
 		}
 	}
 	ExecutedInstruction.fire(*this);
+	assert(cycles() % 4 == 0);
 	return cycles();
 }