From be7c5c64c6a55660d1bdbb23cd5a2f93f4d3a3c8 Mon Sep 17 00:00:00 2001
From: Samuel Perrouault <samuel.perrouault@gmail.com>
Date: Wed, 26 Mar 2025 22:44:04 +0100
Subject: implement LD F, Vx and embed a font

---
 src/lib.rs | 28 ++++++++++++++++++++++++++--
 1 file changed, 26 insertions(+), 2 deletions(-)

(limited to 'src')

diff --git a/src/lib.rs b/src/lib.rs
index 4671be9..37c7914 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -4,6 +4,24 @@ use std::io::Write;
 const WIDTH: u16 = 64;
 const HEIGHT: u16 = 32;
 const PIXELS: usize = (WIDTH * HEIGHT) as usize;
+const FONT: [u8; 80] = [
+    0xF0, 0x90, 0x90, 0x90, 0xF0, //0
+    0x20, 0x60, 0x20, 0x20, 0x70, //1
+    0xF0, 0x10, 0xF0, 0x80, 0xF0, //2
+    0xF0, 0x10, 0xF0, 0x10, 0xF0, //3
+    0x90, 0x90, 0xF0, 0x10, 0x10, //4
+    0xF0, 0x80, 0xF0, 0x10, 0xF0, //5
+    0xF0, 0x80, 0xF0, 0x90, 0xF0, //6
+    0xF0, 0x10, 0x20, 0x40, 0x40, //7
+    0xF0, 0x90, 0xF0, 0x90, 0xF0, //8
+    0xF0, 0x90, 0xF0, 0x10, 0xF0, //9
+    0xF0, 0x90, 0xF0, 0x90, 0x90, //A
+    0xE0, 0x90, 0xE0, 0x90, 0xE0, //B
+    0xF0, 0x80, 0x80, 0x80, 0xF0, //C
+    0xE0, 0x90, 0x90, 0x90, 0xE0, //D
+    0xF0, 0x80, 0xF0, 0x80, 0xF0, //E
+    0xF0, 0x80, 0xF0, 0x80, 0x80, //F
+];
 
 fn unknown_opcode(opcode: u16) {
     eprintln!("Unknwown opcode {:#06x}", opcode);
@@ -48,7 +66,7 @@ pub struct Chip8 {
 
 impl Chip8 {
     pub fn new() -> Self {
-        Self {
+        let mut r = Self {
             v: [0; 16],
             i: 0,
             pc: 0x200,
@@ -61,7 +79,9 @@ impl Chip8 {
             key: [0; 16],
             draw: false,
             random: RandomGenerator::new(),
-        }
+        };
+        r.memory[..80].copy_from_slice(&FONT);
+        r
     }
 
     pub fn load_rom<R: Read>(&mut self, mut reader: R) -> std::io::Result<()> {
@@ -236,6 +256,10 @@ impl Chip8 {
                     eprintln!("ADD, I, V{}", x);
                     self.i += self.v[x] as u16;
                 }
+                0x0029 => {
+                    eprintln!("LD F, V{}", x);
+                    self.i = x as u16 * 5;
+                }
                 0x0033 => {
                     eprintln!("LD, B, V{}", x);
                     let i = self.i as usize;
-- 
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