From 214b8c5266b548009eacda6672ea1d2cff437585 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jo=C3=A3o=20Magalh=C3=A3es?= <joamag@gmail.com>
Date: Sat, 25 Jun 2022 15:50:59 +0100
Subject: [PATCH] feat: initial opcode implementation
---
src/cpu.rs | 55 ++++++++++++++++++++++++++++++++++++++++++------------
1 file changed, 43 insertions(+), 12 deletions(-)
diff --git a/src/cpu.rs b/src/cpu.rs
index eea9197d..f655d593 100644
--- a/src/cpu.rs
+++ b/src/cpu.rs
@@ -1,4 +1,13 @@
-const RAM_SIZE: usize = 8192;
+pub const RAM_SIZE: usize = 8192;
+
+pub const INSTRUCTIONS: [(fn(&mut Cpu), u8, &'static str); 4] = [
+ // 0x0 opcodes
+ (nop, 4, "NOP"),
+ (ld_bc_u16, 12, "LD BC, NN"),
+ (ld_bc_a, 8, "LD BC, A"),
+ // 0x2 opcodes
+ (ld_sp_u16, 12, "LD SP, NN"),
+];
pub struct Cpu {
pc: u16,
@@ -36,13 +45,6 @@ impl Cpu {
// the PC (program counter) accordingly
let instruction = self.ram[self.pc as usize];
self.pc += 1;
-
- let opcode = instruction & 0xf000;
- let address = instruction & 0x0fff;
- let x = ((instruction & 0x0f00) >> 8) as usize;
- let y = ((instruction & 0x00f0) >> 4) as usize;
- let nibble = (instruction & 0x000f) as u8;
- let byte = (instruction & 0x00ff) as u8;
}
#[inline(always)]
@@ -66,22 +68,51 @@ impl Cpu {
}
#[inline(always)]
- fn zero_flag(&self) -> bool {
+ fn read_u8(&mut self) -> u8 {
+ let byte = self.ram[self.pc as usize];
+ self.pc += 1;
+ byte
+ }
+
+ #[inline(always)]
+ fn read_u16(&mut self) -> u16 {
+ let word = (self.ram[self.pc as usize] as u16) << 8 | self.ram[self.pc as usize + 1] as u16;
+ self.pc += 2;
+ word
+ }
+
+ #[inline(always)]
+ fn get_zero(&self) -> bool {
self.reg_f & 0x40 == 1
}
#[inline(always)]
- fn sub_flag(&self) -> bool {
+ fn get_sub(&self) -> bool {
self.reg_f & 0x20 == 1
}
#[inline(always)]
- fn half_carry_flag(&self) -> bool {
+ fn get_half_carry(&self) -> bool {
self.reg_f & 0x10 == 1
}
#[inline(always)]
- fn carry_flag(&self) -> bool {
+ fn get_carry(&self) -> bool {
self.reg_f & 0x08 == 1
}
}
+
+fn nop(_cpu: &mut Cpu) {}
+
+fn ld_bc_u16(cpu: &mut Cpu) {
+ cpu.reg_b = cpu.read_u8();
+ cpu.reg_c = cpu.read_u8();
+}
+
+fn ld_bc_a(cpu: &mut Cpu) {
+ cpu.ram[cpu.reg_bc() as usize] = cpu.reg_a;
+}
+
+fn ld_sp_u16(cpu: &mut Cpu) {
+ cpu.sp = cpu.read_u16();
+}
--
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