From d5bb94cc655d4410544394478587d36b1041d9d3 Mon Sep 17 00:00:00 2001
From: Paul Duncan <pabs@pablotron.org>
Date: Sun, 27 May 2018 10:11:18 -0400
Subject: add initial mmu code

---
 ops.yaml | 191 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 181 insertions(+), 10 deletions(-)

(limited to 'ops.yaml')

diff --git a/ops.yaml b/ops.yaml
index ed60519..360fadb 100644
--- a/ops.yaml
+++ b/ops.yaml
@@ -1779,7 +1779,6 @@ ops:
         c:
       code: |
         ctx->cpu.state = STATE_HALT;
-        cpu_ww(ctx, RW_PC, old_pc); // FIXME?
     - id: LD (HL), A
       hex: 0x77
       cat: "8-bit load/store/move"
@@ -7562,8 +7561,21 @@ templates:
 
     typedef struct {
       struct {
-        // TODO
-        uint8_t mem[0xFFFF];
+        bool in_bios;
+
+        // FIXME: combine these?
+        uint8_t bios[0x100]; // bios (256 bytes)
+        uint8_t ram[0x2000]; // working ram (8k)
+        uint8_t vram[0x2000]; // vram (8k)
+        uint8_t oam[0xA0]; // oam (160 bytes)
+        uint8_t zram[0x7F]; // zram (128 bytes)
+
+        // rom (at least 32k)
+        uint8_t *rom;
+        uint32_t rom_size;
+
+        // external ram (optional, 8k)
+        uint8_t *eram;
       } mmu;
 
       struct {
@@ -7576,10 +7588,93 @@ templates:
 
     static uint8_t
     mmu_rb(
-      const gb_t * const ctx,
+      gb_t * const ctx,
       const uint16_t addr
     ) {
-      return ctx->mmu.mem[addr];
+      switch (addr & 0xF000) {
+      case 0x0000:
+        // bios memory (maybe)
+        if (ctx->mmu.in_bios) {
+          if (addr < 0x100) {
+            return ctx->mmu.bios[addr];
+          } else {
+            ctx->mmu.in_bios = false;
+          }
+        }
+
+        // return ROM0 (16k, always mapped)
+        return ctx->mmu.rom[addr];
+
+        break;
+      case 0x1000:
+      case 0x2000:
+      case 0x3000:
+        // return ROM0 (16k, always mapped)
+        return ctx->mmu.rom[addr];
+        break;
+      case 0x4000:
+      case 0x5000:
+      case 0x6000:
+      case 0x7000:
+        // return ROM1 (16k, banked)
+        // TODO:
+        return ctx->mmu.rom[addr];
+        break;
+      case 0x8000:
+      case 0x9000:
+        // return vram (8k)
+        return ctx->mmu.vram[addr & 0x1FFF];
+        break;
+      case 0xA000:
+      case 0xB000:
+        if (ctx->mmu.eram) {
+          // external ram (8k, optional)
+          return ctx->mmu.eram[addr & 0x1FFF];
+        } else {
+          // FIXME: what do we do with no eram?
+          return 0;
+        }
+
+        break;
+      case 0xC000:
+      case 0xD000:
+        // working ram (8k)
+        return ctx->mmu.ram[addr & 0x1FFF];
+        break;
+      case 0xE000:
+        // working ram (shadow)
+        return ctx->mmu.ram[addr & 0x1FFF];
+        break;
+      case 0xF000:
+        switch (addr & 0x0F00) {
+        case 0x0E00:
+          if (addr < 0xFEA0) {
+            // oam memory (160 bytes):
+            return ctx->mmu.oam[addr & 0xFF];
+          } else {
+            // rest of page reads as zero
+            return 0;
+          }
+
+          break;
+        case 0x0F00:
+          if (addr < 0xFF80) {
+            // TODO: io ports
+            return 0;
+          } else {
+            // zero page
+            return ctx->mmu.zram[addr & 0x7F];
+          }
+
+          break;
+        default:
+          // working ram (shadow)
+          return ctx->mmu.ram[addr & 0x1FFF];
+        }
+      default:
+        // never reached
+        return 0;
+      }
     }
 
     static void
@@ -7588,16 +7683,91 @@ templates:
       const uint16_t addr,
       const uint8_t val
     ) {
-      ctx->mmu.mem[addr] = val;
+      switch (addr & 0xF000) {
+      case 0x0000:
+        // bios memory (maybe)
+        if (ctx->mmu.in_bios) {
+          if (addr < 0x100) {
+            // ctx->mmu.bios[addr];
+          } else {
+            // ctx->mmu.in_bios = false;
+          }
+        }
+
+        // ROM0 (16k, always mapped)
+        // return ctx->rom[addr];
+
+        break;
+      case 0x1000:
+      case 0x2000:
+      case 0x3000:
+        // ROM0 (16k, always mapped)
+        // return ctx->rom[addr];
+        break;
+      case 0x4000:
+      case 0x5000:
+      case 0x6000:
+      case 0x7000:
+        // ROM1 (16k, banked)
+        // return ctx->mmu.rom[addr];
+        break;
+      case 0x8000:
+      case 0x9000:
+        // vram (8k)
+        // FIXME: can we write directly to vram?
+        // return ctx->mmu.vram[addr & 0x1FFF];
+        break;
+      case 0xA000:
+      case 0xB000:
+        if (ctx->mmu.eram) {
+          // external ram (8k, optional)
+          ctx->mmu.eram[addr & 0x1FFF] = val;
+        }
+
+        break;
+      case 0xC000:
+      case 0xD000:
+        // working ram (8k)
+        ctx->mmu.ram[addr & 0x1FFF] = val;
+
+        break;
+      case 0xE000:
+        // working ram (shadow)
+        ctx->mmu.ram[addr & 0x1FFF] = val;
+
+        break;
+      case 0xF000:
+        switch (addr & 0x0F00) {
+        case 0x0E00:
+          if (addr < 0xFEA0) {
+            // oam memory (160 bytes):
+            ctx->mmu.oam[addr & 0xFF] = val;
+          }
+
+          break;
+        case 0x0F00:
+          if (addr < 0xFF80) {
+            // TODO: io ports
+          } else {
+            // zero page
+            ctx->mmu.zram[addr & 0x7F] = val;
+          }
+
+          break;
+        default:
+          // working ram (shadow)
+          ctx->mmu.ram[addr & 0x1FFF] = val;
+        }
+      }
     }
 
     static uint16_t
     mmu_rw(
-      const gb_t * const ctx,
+      gb_t * const ctx,
       const uint16_t addr
     ) {
       // FIXME
-      return (((uint16_t) mmu_rb(ctx, addr)) << 8) + mmu_rb(ctx, addr + 1);
+      return (((uint16_t) mmu_rb(ctx, addr + 1)) << 8) + mmu_rb(ctx, addr);
     }
 
     static void
@@ -7606,8 +7776,9 @@ templates:
       const uint16_t addr,
       const uint16_t val
     ) {
-      ctx->mmu.mem[addr] = (val >> 8);
-      ctx->mmu.mem[addr + 1] = val & 0xFF;
+      // write lsb, msb (little endian)
+      mmu_wb(ctx, addr, val & 0xFF);
+      mmu_wb(ctx, addr + 1, val >> 8);
     }
 
     static uint16_t
-- 
cgit v1.2.3