From 825cdb8788391b7afc8bb92845314f6c0d73ff12 Mon Sep 17 00:00:00 2001
From: NewRisingSun <8vytz1+dhp372pv94ebg@sharklasers.com>
Date: Wed, 14 Apr 2021 21:03:59 +0200
Subject: [PATCH] Add lock bit, necessary for NT-234's Road Fighter

---
 src/boards/addrlatch.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/src/boards/addrlatch.c b/src/boards/addrlatch.c
index 1cd7a26..e46b9ee 100644
--- a/src/boards/addrlatch.c
+++ b/src/boards/addrlatch.c
@@ -108,6 +108,12 @@ static DECLFR(BMCD1038Read) {
 		return CartBR(A);
 }
 
+static DECLFW(BMCD1038Write) {
+	/* Only recognize the latch write if the lock bit has not been set. Needed for NT-234 "Road Fighter" */
+	if (~latche & 0x200)
+		LatchWrite(A, V);
+}
+
 static void BMCD1038Reset(void) {
 	dipswitch++;
 	dipswitch &= 3;
@@ -117,9 +123,17 @@ static void BMCD1038Reset(void) {
 	BMCD1038Sync();
 }
 
+static void BMCD1038Power(void) {
+	LatchPower();
+	
+	/* Trap latch writes to enforce the "Lock" bit */
+	SetWriteHandler(0x8000, 0xFFFF, BMCD1038Write);
+}
+
 void BMCD1038_Init(CartInfo *info) {
 	Latch_Init(info, BMCD1038Sync, BMCD1038Read, 0x0000, 0x8000, 0xFFFF, 0);
 	info->Reset = BMCD1038Reset;
+	info->Power = BMCD1038Power;
 	AddExState(&dipswitch, 1, 0, "DIPSW");
 }