From 8410cd184a1acce652338b09a5469df656b0db2b Mon Sep 17 00:00:00 2001
From: Nathaniel Walizer <robots.are.love@gmail.com>
Date: Fri, 29 Nov 2024 20:26:32 -0800
Subject: [PATCH] Finish PPU memory mapping

---
 Makefile   |  2 +-
 src/nese.c |  8 +++++++-
 src/ppu.c  | 47 ++++++++++++++++++++++++++++++++++++++++-------
 src/ppu.h  |  4 ++++
 4 files changed, 52 insertions(+), 9 deletions(-)

diff --git a/Makefile b/Makefile
index 84620c9..5288a9d 100644
--- a/Makefile
+++ b/Makefile
@@ -1,6 +1,6 @@
 CC = gcc
 LD = $(CC)
-CFLAGS = -Wall -Werror -Wshadow -I.. -g #-DE6502_DEBUG
+CFLAGS = -Wall -Werror -Wshadow -I.. -g -DE6502_DEBUG
 LDFLAGS =
 
 OBJDIR = obj
diff --git a/src/nese.c b/src/nese.c
index 9d4be47..babc6ee 100644
--- a/src/nese.c
+++ b/src/nese.c
@@ -1,3 +1,6 @@
+#include <limits.h>
+#include <stdlib.h>
+
 #include "ines.h"
 
 
@@ -36,6 +39,9 @@ static nes sys = {0};
 int main(int argc, char* argv[]) {
     int status = 0;
 
+    int n_loops = (argc > 1) ? atoi(argv[1]) : 0;
+    if (n_loops <= 0) n_loops = INT_MAX;
+
     status = ines_load(&sys.cart.rom, stdin);
 
     if (status == 0) {
@@ -43,7 +49,7 @@ int main(int argc, char* argv[]) {
         nes_reset(&sys);
 
         int total_cycles = 0;
-        for (int i = 0; i < 15000; ++i) {
+        for (int i = 0; i < n_loops && status == 0; ++i) {
             int run = 0;
             status = nes_run(&sys, 1000, &run);
             total_cycles += run;
diff --git a/src/ppu.c b/src/ppu.c
index a760ae7..cc5ed9a 100644
--- a/src/ppu.c
+++ b/src/ppu.c
@@ -3,8 +3,8 @@
 #include "ppu.h"
 
 
-// TODO: Stubbed
-// TODO: Retain open bus bits
+// TODO: Retain open bus bits?
+
 
 #define ppu_reg_ctrl    (0x2000U)
 #define ppu_reg_mask    (0x2001U)
@@ -29,8 +29,22 @@ uint8_t nes_ppu_read(nes_ppu* ppu, uint16_t addr) {
 
     } else if (ppu_reg_data == addr) {
         val = ppu->data;
-        ppu->data = ppu->vram[ppu->addr -
-                                     nes_ppu_mem_vram_start];
+
+        if (ppu->addr < nes_ppu_mem_vram_start) {
+            ppu->data = ppu->chr_mem[ppu->addr];
+        } else if (ppu->addr < nes_ppu_mem_vram_start +
+                               nes_ppu_mem_vram_size) {
+            ppu->data = ppu->vram[ppu->addr -
+                                  nes_ppu_mem_vram_start];
+        } else if (ppu->addr < nes_ppu_mem_pal_start) {
+            ppu->data = ppu->chr_mem[ppu->addr];
+        } else if (ppu->addr < nes_ppu_mem_size) {
+            uint8_t pal_addr =
+                    (ppu->addr - nes_ppu_mem_pal_start) &
+                    (nes_ppu_mem_pal_size - 1);
+            ppu->data = ppu->palette[pal_addr];
+        }
+
         ppu->addr += (ppu->status & ppu_Control_VRAM_Inc) ?
                      32 : 1;
     }
@@ -68,16 +82,35 @@ void nes_ppu_write(nes_ppu* ppu, uint16_t addr, uint8_t val) {
 
     } else if (ppu_reg_addr == addr) {
         if (ppu->latch) {
-            ppu->addr &= 0xFF00U;
+            ppu->addr &= 0x3F00U;
             ppu->addr |= val;
+            printf("PPU: VRAM ADDR %04x\n", ppu->addr);
+
         } else {
             ppu->addr &= 0x00FFU;
-            ppu->addr |= (uint16_t)(val & 0x3FU) << 8;
+            ppu->addr |= (uint16_t)val << 8;
         }
         ppu->latch = !ppu->latch;
 
     } else if (ppu_reg_data == addr) {
-        ppu->vram[ppu->addr - nes_ppu_mem_vram_start] = val;
+        if (ppu->addr >= nes_ppu_mem_size) {
+            printf("!!! PPU: MEM OOB: %04x", ppu->addr);
+
+        } else if (ppu->addr >= nes_ppu_mem_pal_start) {
+            uint8_t pal_addr =
+                    (ppu->addr - nes_ppu_mem_pal_start) &
+                    (nes_ppu_mem_pal_size - 1);
+            ppu->palette[pal_addr] = val;
+
+        } else if (ppu->addr >= nes_ppu_mem_vram_start) {
+            uint16_t vram_addr = ppu->addr - nes_ppu_mem_vram_start;
+            if (vram_addr >= nes_ppu_mem_vram_size) {
+                printf("!!! PPU: VRAM OOB: %04x", vram_addr);
+                vram_addr &= (nes_ppu_mem_vram_size - 1);
+            }
+            ppu->vram[vram_addr] = val;
+        }
+
         ppu->addr += (ppu->status & ppu_Control_VRAM_Inc) ?
                      32 : 1;
     }
diff --git a/src/ppu.h b/src/ppu.h
index 2ae3308..798240d 100644
--- a/src/ppu.h
+++ b/src/ppu.h
@@ -10,6 +10,9 @@
 #define nes_ppu_postrender  (1U)
 #define nes_ppu_vblank      (20U)
 
+#define nes_ppu_mem_size        (0x4000U)
+#define nes_ppu_mem_pal_start   (0x3F00U)
+#define nes_ppu_mem_pal_size    (0x0020U)
 #define nes_ppu_mem_vram_start  (0x2000U)
 #define nes_ppu_mem_vram_size   (0x0800U)
 
@@ -36,6 +39,7 @@ typedef struct {
     uint8_t* chr_mem;
     uint8_t oam[nes_ppu_oam_size];
     uint8_t vram[nes_ppu_mem_vram_size];
+    uint8_t palette[nes_ppu_mem_pal_size];
 
     int frame;
     int scanline;