From b0c690c6938a46d3a2511a2cb3e2c90aa0c6f36b Mon Sep 17 00:00:00 2001
From: Matthew Laux <matthew.laux@gmail.com>
Date: Mon, 20 Jun 2022 19:46:32 -0500
Subject: [PATCH] update lcd every 456 cycles

---
 cli/emulator.c |  3 ++-
 src/cpu.c      | 15 ++++++++++-----
 src/dmg.c      |  4 ++--
 src/lcd.c      |  1 +
 4 files changed, 15 insertions(+), 8 deletions(-)

diff --git a/cli/emulator.c b/cli/emulator.c
index 402245d..92e2e3b 100644
--- a/cli/emulator.c
+++ b/cli/emulator.c
@@ -32,7 +32,8 @@ int main(int argc, char *argv[])
 
     cpu.pc = 0;
 
-    for (executed = 0; executed < 100000; executed++) {
+    // for (executed = 0; executed < 100000; executed++) {
+    while (1) {
         dmg_step(&dmg);
     }
 
diff --git a/src/cpu.c b/src/cpu.c
index 5970285..7b5c6ae 100644
--- a/src/cpu.c
+++ b/src/cpu.c
@@ -300,6 +300,9 @@ static void extended_insn(struct cpu *cpu, u8 insn)
         shift_right // TODO SRL
     };
 
+    printf("       %s\n", instructions[insn + 0x100].format);
+    cpu->cycle_count += instructions[insn + 0x100].cycles;
+
     switch (op) {
         case 0:
             write_reg(cpu, reg, funcs[bit](cpu, read_reg(cpu, reg)));
@@ -330,6 +333,7 @@ void cpu_step(struct cpu *cpu)
     u8 opc = cpu->mem_read(cpu->mem_model, cpu->pc);
     printf("0x%04x %s\n", cpu->pc, instructions[opc].format);
     cpu->pc++;
+    cpu->cycle_count += instructions[opc].cycles;
     switch (opc) {
         case 0: // NOP
             break;
@@ -500,6 +504,7 @@ void cpu_step(struct cpu *cpu)
             temp = read8(cpu, cpu->pc);
             if ((opc == 0x20) ^ flag_isset(cpu, FLAG_ZERO)) {
                 cpu->pc += *((signed char *) &temp) + 1;
+                cpu->cycle_count += instructions[opc].cycles_branch - instructions[opc].cycles;
             } else {
                 cpu->pc++;
             }
@@ -650,19 +655,19 @@ void cpu_step(struct cpu *cpu)
             add(cpu, read8(cpu, cpu->pc), 1);
             cpu->pc++;
             break;
-        case 0xe0: // LDH (a8),A
-            write16(cpu, 0xff00 + read8(cpu, cpu->pc), cpu->a);
+        case 0xe0: // LD (a8),A
+            write8(cpu, 0xff00 + read8(cpu, cpu->pc), cpu->a);
             cpu->pc++;
             break;
         case 0xe2: // LD (C),A
             write8(cpu, 0xff00 + cpu->c, cpu->a);
             break;
         case 0xea: // LD (a16),A
-            write16(cpu, read16(cpu, cpu->pc), cpu->a);
+            write8(cpu, read16(cpu, cpu->pc), cpu->a);
             cpu->pc += 2;
             break;
-        case 0xf0: // LDH A,(a8)
-            cpu->a = read16(cpu, 0xff00 + read8(cpu, cpu->pc));
+        case 0xf0: // LD A,(a8)
+            cpu->a = read8(cpu, 0xff00 + read8(cpu, cpu->pc));
             cpu->pc++;
             break;
         case 0xf2: // LD A,(C)
diff --git a/src/dmg.c b/src/dmg.c
index 8dca22d..3794907 100644
--- a/src/dmg.c
+++ b/src/dmg.c
@@ -75,8 +75,8 @@ void dmg_step(void *_dmg)
     // all other hw
     cpu_step(dmg->cpu);
 
-    if (dmg->cpu->pc % 456 == 0) {
-        // each line takes 456 cycles
+    // each line takes 456 cycles
+    if (dmg->cpu->cycle_count % 456 == 0) {
         lcd_step(dmg->lcd);
     }
 }
\ No newline at end of file
diff --git a/src/lcd.c b/src/lcd.c
index d482d1f..21b682e 100644
--- a/src/lcd.c
+++ b/src/lcd.c
@@ -49,4 +49,5 @@ void lcd_step(struct lcd *lcd)
     // step to next scanline 0-153
     u8 next_scanline = (lcd_read(lcd, REG_LY) + 1) % 154;
     lcd_write(lcd, REG_LY, next_scanline);
+    // printf("update lcd %d\n", next_scanline);
 }
\ No newline at end of file