From d2b66e9cb524df635e44b9853785c3e59857273e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jo=C3=A3o=20Magalh=C3=A3es?= <joamag@gmail.com>
Date: Sat, 18 Jun 2022 19:33:14 +0100
Subject: [PATCH] feat: initial instruction processing
---
src/chip8_neo.rs | 25 +++++++++++++++++++++++++
1 file changed, 25 insertions(+)
diff --git a/src/chip8_neo.rs b/src/chip8_neo.rs
index ab88193..3683ef2 100644
--- a/src/chip8_neo.rs
+++ b/src/chip8_neo.rs
@@ -59,7 +59,28 @@ impl Chip8Neo {
}
pub fn tick(&mut self) {
+ // fetches the current instruction and increments
+ // the PC (program counter) accordingly
+ let instruction =
+ (self.ram[self.pc as usize] as u16) << 8 | self.ram[self.pc as usize + 1] as u16;
self.pc += 0x2;
+
+ let opcode = instruction & 0xf000;
+ let address = instruction & 0x0fff;
+ let nibble = ((instruction & 0x0f00) >> 8) as u8;
+ let byte = (instruction & 0x00ff) as u8;
+
+ match opcode {
+ 0x0000 => match byte {
+ 0xe0 => self.clear_screen(),
+ _ => println!("unimplemented instruction"),
+ },
+ 0x1000 => self.pc = address,
+ 0x6000 => {
+ self.registers[nibble as usize] = byte;
+ }
+ _ => println!("unimplemented instruction"),
+ }
}
pub fn load_rom(&mut self, rom: &[u8]) {
@@ -73,4 +94,8 @@ impl Chip8Neo {
fn load_default_font(&mut self) {
self.load_font(0, &FONT_SET);
}
+
+ fn clear_screen(&mut self) {
+ self.vram = [0u8; DISPLAY_WIDTH * DISPLAY_HEIGHT];
+ }
}
--
GitLab