chore: add new constants for ADDR values

Also made some initial timer validation.

src/consts.rs

+// Timer registers
+pub const DIV_ADDR: u16 = 0xff04;
+pub const TIMA_ADDR: u16 = 0xff05;
+pub const TMA_ADDR: u16 = 0xff06;
+pub const TAC_ADDR: u16 = 0xff07;

src/lib.rs

@@ -2,6 +2,7 @@
 
 pub mod apu;
 pub mod cheats;
+pub mod consts;
 pub mod cpu;
 pub mod data;
 pub mod devices;

src/test.rs

@@ -65,11 +65,13 @@ pub fn run_image_test(
 
 #[cfg(test)]
 mod tests {
+    use crate::consts::{DIV_ADDR, TAC_ADDR, TIMA_ADDR, TMA_ADDR};
+
     use super::{run_serial_test, run_step_test, TestOptions};
 
     #[test]
     fn test_boot_state() {
-        let result = run_step_test(
+        let mut result = run_step_test(
             "res/roms/test/blargg/cpu/cpu_instrs.gb",
             0x0100,
             TestOptions::default(),
@@ -81,6 +83,11 @@ mod tests {
         assert_eq!(result.cpu_i().de(), 0x00d8);
         assert_eq!(result.cpu_i().hl(), 0x014d);
         assert_eq!(result.cpu_i().ime(), false);
+
+        assert_eq!(result.mmu().read(DIV_ADDR), 0xab);
+        assert_eq!(result.mmu().read(TIMA_ADDR), 0x00);
+        assert_eq!(result.mmu().read(TMA_ADDR), 0x00);
+        assert_eq!(result.mmu().read(TAC_ADDR), 0xf8);
     }
 
     #[test]

src/timer.rs

-use crate::warnln;
+use crate::{
+    consts::{DIV_ADDR, TAC_ADDR, TIMA_ADDR, TMA_ADDR},
+    warnln,
+};
 
 pub struct Timer {
     div: u8,
@@ -70,13 +73,13 @@ impl Timer {
     pub fn read(&mut self, addr: u16) -> u8 {
         match addr {
             // 0xFF04 — DIV: Divider register
-            0xff04 => self.div,
+            DIV_ADDR => self.div,
             // 0xFF05 — TIMA: Timer counter
-            0xff05 => self.tima,
+            TIMA_ADDR => self.tima,
             // 0xFF06 — TMA: Timer modulo
-            0xff06 => self.tma,
+            TMA_ADDR => self.tma,
             // 0xFF07 — TAC: Timer control
-            0xff07 => self.tac,
+            TAC_ADDR => self.tac | 0xf8,
             _ => {
                 warnln!("Reding from unknown Timer location 0x{:04x}", addr);
                 0xff
@@ -87,13 +90,13 @@ impl Timer {
     pub fn write(&mut self, addr: u16, value: u8) {
         match addr {
             // 0xFF04 — DIV: Divider register
-            0xff04 => self.div = 0,
+            DIV_ADDR => self.div = 0,
             // 0xFF05 — TIMA: Timer counter
-            0xff05 => self.tima = value,
+            TIMA_ADDR => self.tima = value,
             // 0xFF06 — TMA: Timer modulo
-            0xff06 => self.tma = value,
+            TMA_ADDR => self.tma = value,
             // 0xFF07 — TAC: Timer control
-            0xff07 => {
+            TAC_ADDR => {
                 self.tac = value;
                 match value & 0x03 {
                     0x00 => self.tima_ratio = 1024,