Add DMA and SNES Init, VBlank, NMI, etc
This commit is contained in:
scawful
@@ -1,7 +1,9 @@
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#include "snes.h"
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#include <cstdint>
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#include <memory>
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#include <string>
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#include <thread>
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#include "app/emu/apu.h"
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#include "app/emu/cpu.h"
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@@ -12,8 +14,73 @@ namespace yaze {
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namespace app {
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namespace emu {
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void DMA::StartDMATransfer(uint8_t channelMask) {
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for (int i = 0; i < 8; ++i) {
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if ((channelMask & (1 << i)) != 0) {
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Channel& ch = channels[i];
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// Validate channel parameters (e.g., DMAPn, BBADn, A1Tn, DASn)
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// ...
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// Determine the transfer direction based on the DMAPn register
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bool fromMemory = (ch.DMAPn & 0x80) != 0;
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// Determine the transfer size based on the DMAPn register
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bool transferTwoBytes = (ch.DMAPn & 0x40) != 0;
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// Perform the DMA transfer based on the channel parameters
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std::cout << "Starting DMA transfer for channel " << i << std::endl;
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for (uint16_t j = 0; j < ch.DASn; ++j) {
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// Read a byte or two bytes from memory based on the transfer size
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// ...
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// Write the data to the B-bus address (BBADn) if transferring from
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// memory
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// ...
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// Update the A1Tn register based on the transfer direction
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if (fromMemory) {
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ch.A1Tn += transferTwoBytes ? 2 : 1;
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} else {
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ch.A1Tn -= transferTwoBytes ? 2 : 1;
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}
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}
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// Update the channel registers after the transfer (e.g., A1Tn, DASn)
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// ...
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}
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}
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MDMAEN = channelMask; // Set the MDMAEN register to the channel mask
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}
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void DMA::EnableHDMATransfers(uint8_t channelMask) {
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for (int i = 0; i < 8; ++i) {
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if ((channelMask & (1 << i)) != 0) {
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Channel& ch = channels[i];
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// Validate channel parameters (e.g., DMAPn, BBADn, A1Tn, A2An, NLTRn)
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// ...
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// Perform the HDMA setup based on the channel parameters
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std::cout << "Enabling HDMA transfer for channel " << i << std::endl;
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// Read the HDMA table from memory starting at A1Tn
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// ...
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// Update the A2An register based on the HDMA table
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// ...
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// Update the NLTRn register based on the HDMA table
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// ...
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}
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}
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HDMAEN = channelMask; // Set the HDMAEN register to the channel mask
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}
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void SNES::Init(ROM& rom) {
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// Initialize CPU
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// Perform a long jump into a FastROM bank (if the ROM speed is FastROM)
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// Disable the emulation flag (switch to 65816 native mode)s
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cpu.Init();
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// Initialize PPU
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@@ -22,8 +89,95 @@ void SNES::Init(ROM& rom) {
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// Initialize APU
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apu.Init();
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// Load ROM
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// Disable interrupts and rendering
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memory_.WriteByte(0x4200, 0x00); // NMITIMEN
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memory_.WriteByte(0x420C, 0x00); // HDMAEN
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// Disable screen
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memory_.WriteByte(0x2100, 0x8F); // INIDISP
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// Fill Work-RAM with zeros using two 64KiB fixed address DMA transfers to
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// WMDATA
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// TODO: Make this load from work ram, potentially in Memory class
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std::memset((void*)memory_.ram_.data(), 0, sizeof(memory_.ram_));
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// Reset PPU registers to a known good state
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memory_.WriteByte(0x4201, 0xFF); // WRIO
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// Objects
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memory_.WriteByte(0x2101, 0x00); // OBSEL
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memory_.WriteByte(0x2102, 0x00); // OAMADDL
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memory_.WriteByte(0x2103, 0x00); // OAMADDH
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// Backgrounds
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memory_.WriteByte(0x2105, 0x00); // BGMODE
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memory_.WriteByte(0x2106, 0x00); // MOSAIC
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memory_.WriteByte(0x2107, 0x00); // BG1SC
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memory_.WriteByte(0x2108, 0x00); // BG2SC
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memory_.WriteByte(0x2109, 0x00); // BG3SC
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memory_.WriteByte(0x210A, 0x00); // BG4SC
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memory_.WriteByte(0x210B, 0x00); // BG12NBA
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memory_.WriteByte(0x210C, 0x00); // BG34NBA
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// Scroll Registers
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memory_.WriteByte(0x210D, 0x00); // BG1HOFS
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memory_.WriteByte(0x210E, 0xFF); // BG1VOFS
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memory_.WriteByte(0x210F, 0x00); // BG2HOFS
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memory_.WriteByte(0x2110, 0xFF); // BG2VOFS
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memory_.WriteByte(0x2111, 0x00); // BG3HOFS
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memory_.WriteByte(0x2112, 0xFF); // BG3VOFS
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memory_.WriteByte(0x2113, 0x00); // BG4HOFS
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memory_.WriteByte(0x2114, 0xFF); // BG4VOFS
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// VRAM Registers
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memory_.WriteByte(0x2115, 0x80); // VMAIN
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// Mode 7
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memory_.WriteByte(0x211A, 0x00); // M7SEL
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memory_.WriteByte(0x211B, 0x01); // M7A
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memory_.WriteByte(0x211C, 0x00); // M7B
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memory_.WriteByte(0x211D, 0x00); // M7C
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memory_.WriteByte(0x211E, 0x01); // M7D
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memory_.WriteByte(0x211F, 0x00); // M7X
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memory_.WriteByte(0x2120, 0x00); // M7Y
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// Windows
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memory_.WriteByte(0x2123, 0x00); // W12SEL
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memory_.WriteByte(0x2124, 0x00); // W34SEL
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memory_.WriteByte(0x2125, 0x00); // WOBJSEL
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memory_.WriteByte(0x2126, 0x00); // WH0
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memory_.WriteByte(0x2127, 0x00); // WH1
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memory_.WriteByte(0x2128, 0x00); // WH2
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memory_.WriteByte(0x2129, 0x00); // WH3
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memory_.WriteByte(0x212A, 0x00); // WBGLOG
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memory_.WriteByte(0x212B, 0x00); // WOBJLOG
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// Layer Enable
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memory_.WriteByte(0x212C, 0x00); // TM
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memory_.WriteByte(0x212D, 0x00); // TS
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memory_.WriteByte(0x212E, 0x00); // TMW
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memory_.WriteByte(0x212F, 0x00); // TSW
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// Color Math
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memory_.WriteByte(0x2130, 0x30); // CGWSEL
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memory_.WriteByte(0x2131, 0x00); // CGADSUB
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memory_.WriteByte(0x2132, 0xE0); // COLDATA
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// Misc
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memory_.WriteByte(0x2133, 0x00); // SETINI
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// Load ROM data into memory
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// TODO: Load memory based on memory mapping and ROM format.
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memory_.SetMemory(rom.vector());
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// Initialize other private member variables
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running_ = true;
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scanline = 0;
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}
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void SNES::Run() {
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@@ -81,6 +235,60 @@ void SNES::Run() {
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}
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}
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// Enable NMI Interrupts
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void SNES::EnableVBlankInterrupts() {
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vBlankFlag = 0;
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// Clear the RDNMI VBlank flag
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memory_.ReadByte(0x4210); // RDNMI
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// Enable vblank NMI interrupts and Joypad auto-read
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memory_.WriteByte(0x4200, 0x81); // NMITIMEN
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}
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// Wait until the VBlank routine has been processed
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void SNES::WaitForVBlank() {
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vBlankFlag = 1;
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// Loop until `vBlankFlag` is clear
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while (vBlankFlag) {
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std::this_thread::yield();
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}
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}
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// NMI Interrupt Service Routine
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void SNES::NmiIsr() {
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// Switch to a FastROM bank (assuming NmiIsr is in bank 0x80)
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// ...
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// Push CPU registers to stack
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cpu.PHP();
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// Reset DB and DP registers
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cpu.DB = 0x80; // Assuming bank 0x80, can be changed to 0x00
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cpu.D = 0;
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if (vBlankFlag) {
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VBlankRoutine();
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// Clear `vBlankFlag`
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vBlankFlag = false;
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}
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// Increment 32-bit frameCounter
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frameCounter++;
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// Restore CPU registers
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cpu.PHB();
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}
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// VBlank routine
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void SNES::VBlankRoutine() {
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// Execute code that needs to run during VBlank, such as transferring data to
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// the PPU
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// ...
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}
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void SNES::RenderScanline() {
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// Render background layers
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for (int layer = 0; layer < 4; layer++) {
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