From 399b5d65e50b48c74534526848969a31af7e3896 Mon Sep 17 00:00:00 2001
From: Logan McNaughton <848146+loganmc10@users.noreply.github.com>
Date: Sat, 30 May 2026 09:43:22 +0200
Subject: [PATCH] Fix MBC3 latch (#987)

* Fix MBC3 latch

* more
---
 src/device/controller/gbcart.rs      | 27 +++++++--------------------
 src/device/controller/transferpak.rs |  1 -
 2 files changed, 7 insertions(+), 21 deletions(-)

diff --git a/src/device/controller/gbcart.rs b/src/device/controller/gbcart.rs
index 318b460..2fc9871 100644
--- a/src/device/controller/gbcart.rs
+++ b/src/device/controller/gbcart.rs
@@ -19,7 +19,6 @@ pub struct GbCart {
     pub mbc1_mode: bool,
     pub ram_bank: u16,
     pub rom_bank: u32,
-    pub latch: bool,
     pub rtc_regs: [u8; MBC3_RTC_REGS_COUNT],
     pub rtc_regs_latch: [u8; MBC3_RTC_REGS_COUNT],
     pub last_elapsed_time: i64,
@@ -255,12 +254,9 @@ fn write_mbc3(
     } else if address < 0x6000 {
         cart.ram_bank = (value & 0xf) as u16;
     } else if address < 0x8000 {
-        if cart.cart_type == CartType::MBC3RamBattRtc {
-            if !cart.latch && (value & 0x1) != 0 {
-                update_rtc_regs(cart, elapsed_time);
-                cart.rtc_regs_latch = cart.rtc_regs;
-            }
-            cart.latch = (value & 0x1) != 0;
+        if cart.cart_type == CartType::MBC3RamBattRtc && (value & 0x1) != 0 {
+            update_rtc_regs(cart, elapsed_time);
+            cart.rtc_regs_latch = cart.rtc_regs;
         }
     } else if (0xa000..0xc000).contains(&address) {
         if !cart.ram_enabled {
@@ -284,7 +280,6 @@ fn read_mbc3(
     address: u16,
     data: usize,
     size: usize,
-    elapsed_time: i64,
 ) {
     if address < 0x4000 {
         let banked_address = address & 0x3FFF;
@@ -309,15 +304,8 @@ fn read_mbc3(
                     .unwrap_or(&vec![0; size]),
             );
         } else if cart.cart_type == CartType::MBC3RamBattRtc {
-            if cart.latch {
-                for i in 0..size {
-                    pif_ram[data + i] = cart.rtc_regs_latch[cart.ram_bank as usize - 0x8];
-                }
-            } else {
-                update_rtc_regs(cart, elapsed_time);
-                for i in 0..size {
-                    pif_ram[data + i] = cart.rtc_regs[cart.ram_bank as usize - 0x8];
-                }
+            for i in 0..size {
+                pif_ram[data + i] = cart.rtc_regs_latch[cart.ram_bank as usize - 0x8];
             }
         }
     } else {
@@ -395,7 +383,6 @@ pub fn read(
     address: u16,
     data: usize,
     size: usize,
-    elapsed_time: i64,
 ) {
     if !cart.enabled {
         for i in 0..size {
@@ -405,8 +392,8 @@ pub fn read(
     }
     match cart.cart_type {
         CartType::MBC1RamBatt => read_mbc1(pif_ram, cart, address, data, size),
-        CartType::MBC3RamBatt => read_mbc3(pif_ram, cart, address, data, size, elapsed_time),
-        CartType::MBC3RamBattRtc => read_mbc3(pif_ram, cart, address, data, size, elapsed_time),
+        CartType::MBC3RamBatt => read_mbc3(pif_ram, cart, address, data, size),
+        CartType::MBC3RamBattRtc => read_mbc3(pif_ram, cart, address, data, size),
         CartType::MBC5RamBatt => read_mbc5(pif_ram, cart, address, data, size),
         _ => panic!("Unsupported cart type"),
     }
diff --git a/src/device/controller/transferpak.rs b/src/device/controller/transferpak.rs
index 2505532..ce28291 100644
--- a/src/device/controller/transferpak.rs
+++ b/src/device/controller/transferpak.rs
@@ -58,7 +58,6 @@ pub fn read(device: &mut device::Device, channel: usize, address: u16, data: usi
                 0x4000 * pak.bank + (address & 0x7fff) - 0x4000,
                 data,
                 size,
-                device.vi.elapsed_time as i64,
             );
         }
         _ => {