From ea70b592ce00193dabd55b1bc7a903949930b7a3 Mon Sep 17 00:00:00 2001
From: Theron Spiegl <tspiegl@gmail.com>
Date: Sun, 19 Jan 2020 11:30:51 -0600
Subject: [PATCH] put chr-ram back in mmc1

---
 src/cartridge/mmc1.rs | 32 ++++++++++++++++++--------------
 src/cpu/mod.rs        |  1 -
 2 files changed, 18 insertions(+), 15 deletions(-)

diff --git a/src/cartridge/mmc1.rs b/src/cartridge/mmc1.rs
index cbb07c0..3d7c936 100644
--- a/src/cartridge/mmc1.rs
+++ b/src/cartridge/mmc1.rs
@@ -114,21 +114,25 @@ impl Mapper for Mmc1 {
     fn read(&mut self, address: usize) -> u8 {
         match address {
             0x0000..=0x1FFF => {
-                let offset = address % 0x1000;
-                if self.chr_bank_mode {
-                    // if 4K bank mode, $0000-$0FFF will be a 4K-indexed section of some CHR-ROM chunk referred to by chr_low_bank
-                    // and $1000-$1FFF will be the one referred to by chr_high_bank
-                    let bank = match address {
-                        0x0000..=0x0FFF => self.chr_low_bank,
-                        0x1000..=0x1FFF => self.chr_high_bank,
-                        _ => panic!("bad address read from MMC1: 0x{:X}", address),
-                    };
-                    let chunk_num = bank / 2;
-                    let chunk_half = if bank % 2 == 0 {0x0} else {0x1000};
-                    self.cart.chr_rom[chunk_num][chunk_half + offset]
+                if self.cart.chr_rom_size == 0 {
+                    self.chr_ram_bank[address]
                 } else {
-                    // if we're in 8K bank mode, the whole $0000-$1FFF region will be the 8K range referred to by chr_low_bank
-                    self.cart.chr_rom[self.chr_low_bank][address]
+                    let offset = address % 0x1000;
+                    if self.chr_bank_mode {
+                        // if 4K bank mode, $0000-$0FFF will be a 4K-indexed section of some CHR-ROM chunk referred to by chr_low_bank
+                        // and $1000-$1FFF will be the one referred to by chr_high_bank
+                        let bank = match address {
+                            0x0000..=0x0FFF => self.chr_low_bank,
+                            0x1000..=0x1FFF => self.chr_high_bank,
+                            _ => panic!("bad address read from MMC1: 0x{:X}", address),
+                        };
+                        let chunk_num = bank / 2;
+                        let chunk_half = if bank % 2 == 0 {0x0} else {0x1000};
+                        self.cart.chr_rom[chunk_num][chunk_half + offset]
+                    } else {
+                        // if we're in 8K bank mode, the whole $0000-$1FFF region will be the 8K range referred to by chr_low_bank
+                        self.cart.chr_rom[self.chr_low_bank][address]
+                    }
                 }
             },
             0x6000..=0x7FFF => self.prg_ram_bank[address % 0x2000],
diff --git a/src/cpu/mod.rs b/src/cpu/mod.rs
index 3e9a3a8..42d6203 100644
--- a/src/cpu/mod.rs
+++ b/src/cpu/mod.rs
@@ -156,7 +156,6 @@ impl Cpu {
         self.apu.trigger_irq = false;
         // and mapper MMC3
         if self.mapper.borrow_mut().check_irq() && (self.P & INTERRUPT_DISABLE_FLAG == 0) {
-            // println!("firing IRQ from mapper");
             self.irq();
         }