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tms9918_device.c
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tms9918_device.c
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/*
* Troy's HBC-56 Emulator - TMS9918 device
*
* Copyright (c) 2021 Troy Schrapel
*
* This code is licensed under the MIT license
*
* https://github.com/visrealm/hbc-56/emulator
*
*/
#include "tms9918_device.h"
#include "vrEmuTms9918.h"
#include "vrEmuTms9918Util.h"
#include "../hbc56emu.h"
#include "SDL.h"
#include <stdlib.h>
#include <string.h>
#include <math.h>
static void resetTms9918Device(HBC56Device*);
static void destroyTms9918Device(HBC56Device*);
static void renderTms9918Device(HBC56Device* device);
static void tickTms9918Device(HBC56Device*, uint32_t, float);
static uint8_t readTms9918Device(HBC56Device*, uint16_t, uint8_t*, uint8_t);
static uint8_t writeTms9918Device(HBC56Device*, uint16_t, uint8_t);
/* tms9918 constants */
#define TMS9918_DISPLAY_WIDTH 320
#define TMS9918_DISPLAY_HEIGHT 240
#define TMS9918_FPS 60.0f
#define TMS9918_TICK_MIN_PIXELS 26
/* tms9918 computed constants */
#define TMS9918_FRAME_TIME (1.0f / TMS9918_FPS)
#define TMS9918_ROW_TIME (TMS9918_FRAME_TIME / (float)TMS9918_DISPLAY_HEIGHT)
#define TMS9918_PIXEL_TIME (TMS9918_ROW_TIME / (float)TMS9918_DISPLAY_WIDTH)
#define TMS9918_BORDER_X ((TMS9918_DISPLAY_WIDTH - TMS9918_PIXELS_X) / 2)
#define TMS9918_BORDER_Y ((TMS9918_DISPLAY_HEIGHT - TMS9918_PIXELS_Y) / 2)
#define TMS9918_DISPLAY_PIXELS (TMS9918_DISPLAY_WIDTH * TMS9918_DISPLAY_HEIGHT)
/* tms9918 device data */
struct TMS9918Device
{
uint16_t dataAddr;
uint16_t regAddr;
VrEmuTms9918 *tms9918;
uint32_t frameBuffer[TMS9918_DISPLAY_PIXELS];
float unusedTime;
int currentFramePixels;
uint8_t scanlineBuffer[TMS9918_DISPLAY_WIDTH];
uint8_t irq;
};
typedef struct TMS9918Device TMS9918Device;
/* Function: createTms9918Device
* --------------------
* create a TMS9918 device
*/
HBC56Device createTms9918Device(uint16_t dataAddr, uint16_t regAddr, uint8_t irq, SDL_Renderer* renderer)
{
HBC56Device device = createDevice("TMS9918 VDP");
TMS9918Device* tmsDevice = (TMS9918Device*)malloc(sizeof(TMS9918Device));
if (tmsDevice)
{
tmsDevice->dataAddr = dataAddr;
tmsDevice->regAddr = regAddr;
tmsDevice->irq = irq;
tmsDevice->tms9918 = vrEmuTms9918New();
tmsDevice->unusedTime = 0.0f;
tmsDevice->currentFramePixels = 0;
memset(tmsDevice->frameBuffer, 0, sizeof(tmsDevice->frameBuffer));
memset(tmsDevice->scanlineBuffer, 6, sizeof(tmsDevice->scanlineBuffer));
device.data = tmsDevice;
device.resetFn = &resetTms9918Device;
device.destroyFn = &destroyTms9918Device;
device.readFn = &readTms9918Device;
device.writeFn = &writeTms9918Device;
device.tickFn = &tickTms9918Device;
device.renderFn = &renderTms9918Device;
device.output = SDL_CreateTexture(renderer, SDL_PIXELFORMAT_RGBA8888, SDL_TEXTUREACCESS_STREAMING,
TMS9918_DISPLAY_WIDTH, TMS9918_DISPLAY_HEIGHT);
#ifndef __linux__
SDL_SetTextureScaleMode(device.output, SDL_ScaleModeBest);
#endif
}
else
{
destroyDevice(&device);
}
return device;
}
/* Function: getTms9918Device
* --------------------
* helper funtion to get private structure
*/
inline static TMS9918Device* getTms9918Device(HBC56Device* device)
{
if (!device) return NULL;
return (TMS9918Device*)device->data;
}
/* Function: resetTms9918Device
* --------------------
* called when the machine is reset. resets the tms internal state
*/
static void resetTms9918Device(HBC56Device* device)
{
TMS9918Device* tmsDevice = getTms9918Device(device);
if (tmsDevice)
{
vrEmuTms9918Reset(tmsDevice->tms9918);
}
}
/* Function: destroyTms9918Device
* --------------------
* destroy/clean up the tms data structure
*/
static void destroyTms9918Device(HBC56Device *device)
{
TMS9918Device *tmsDevice = getTms9918Device(device);
if (tmsDevice)
{
vrEmuTms9918Destroy(tmsDevice->tms9918);
}
free(tmsDevice);
device->data = NULL;
SDL_DestroyTexture(device->output);
device->output = NULL;
}
/* Function: renderTms9918Device
* --------------------
* renders the TMS9918 to the output texture
*/
static void renderTms9918Device(HBC56Device* device)
{
TMS9918Device* tmsDevice = getTms9918Device(device);
if (tmsDevice)
{
void *pixels = NULL;
int pitch = 0;
SDL_LockTexture(device->output, NULL, &pixels, &pitch);
memcpy(pixels, tmsDevice->frameBuffer, sizeof(tmsDevice->frameBuffer));
SDL_UnlockTexture(device->output);
}
}
/* Function: tickTms9918Device
* --------------------
* renders the portion of the screen since the last call. relies on deltaTime to determine
* how much of the screen to render. this style of rendering allows mid-frame changes to be
* shown in the display if called frequently enough. you can achieve beam racing effects.
*/
int c = 0;
static void tickTms9918Device(HBC56Device* device, uint32_t deltaTicks, float deltaTime)
{
TMS9918Device* tmsDevice = getTms9918Device(device);
if (tmsDevice)
{
/* determine portion of frame to render */
deltaTime += tmsDevice->unusedTime;
/* how many pixels are we rendering? */
float thisStepTotalPixelsFlt = 0.0f;
tmsDevice->unusedTime = modff(deltaTime / (float)TMS9918_PIXEL_TIME, &thisStepTotalPixelsFlt) * TMS9918_PIXEL_TIME;
int thisStepTotalPixels = (uint32_t)thisStepTotalPixelsFlt;
/* if we haven't reached the minimum, accumulate time for the next call and return */
if (thisStepTotalPixels < TMS9918_TICK_MIN_PIXELS)
{
tmsDevice->unusedTime += thisStepTotalPixels * TMS9918_PIXEL_TIME;
return;
}
/* we only render the end end of a frame. if we need to go further, accumulate the time for the next call */
if (tmsDevice->currentFramePixels + thisStepTotalPixels >= TMS9918_DISPLAY_PIXELS)
{
tmsDevice->unusedTime += ((tmsDevice->currentFramePixels + thisStepTotalPixels) - TMS9918_DISPLAY_PIXELS) * TMS9918_PIXEL_TIME;
thisStepTotalPixels = TMS9918_DISPLAY_PIXELS - tmsDevice->currentFramePixels;
}
/* get the background color for this run of pixels */
uint8_t bgColor = vrEmuTms9918RegValue(tmsDevice->tms9918, TMS_REG_7) & 0x0f;
//bgColor = (++c) & 0x0f; /* for testing */
int firstPix = 1;
uint32_t* fbPtr = tmsDevice->frameBuffer + tmsDevice->currentFramePixels;
int tmsRow = 0;
/* iterate over the pixels we need to update in this call */
for (int p = 0; p < thisStepTotalPixels; ++p)
{
div_t currentPos = div((int)tmsDevice->currentFramePixels, (int)TMS9918_DISPLAY_WIDTH);
int currentRow = currentPos.quot;
int currentCol = currentPos.rem;
/* if this is the first pixel or the first pixel of a new row, update the scanline buffer */
if (firstPix || currentCol == 0)
{
tmsRow = currentRow - TMS9918_BORDER_Y;
memset(tmsDevice->scanlineBuffer, bgColor, sizeof(tmsDevice->scanlineBuffer));
if (tmsRow >=0 && tmsRow < TMS9918_PIXELS_Y)
{
vrEmuTms9918ScanLine(tmsDevice->tms9918, (uint8_t)tmsRow, tmsDevice->scanlineBuffer + TMS9918_BORDER_X);
}
firstPix = 0;
}
/* update the frame buffer pixel from the scanline pixel */
*(fbPtr++) = vrEmuTms9918Palette[tmsDevice->scanlineBuffer[currentCol]];
/* if we're at the end of the main tms9918 frame, trigger an interrupt */
if (++tmsDevice->currentFramePixels == (TMS9918_DISPLAY_WIDTH * (TMS9918_DISPLAY_HEIGHT - TMS9918_BORDER_Y)))
{
if (vrEmuTms9918RegValue(tmsDevice->tms9918, TMS_REG_1) & 0x20)
{
hbc56Interrupt(tmsDevice->irq, INTERRUPT_RAISE);
}
}
}
/* reset pixel count if frame finished */
if (tmsDevice->currentFramePixels >= TMS9918_DISPLAY_PIXELS) tmsDevice->currentFramePixels= 0;
}
}
/* Function: readTms9918Device
* --------------------
* read from the tms. address determines status or data
*/
static uint8_t readTms9918Device(HBC56Device* device, uint16_t addr, uint8_t *val, uint8_t dbg)
{
TMS9918Device* tmsDevice = getTms9918Device(device);
if (tmsDevice && val)
{
if (addr == tmsDevice->regAddr)
{
*val = vrEmuTms9918ReadStatus(tmsDevice->tms9918);
if (!dbg) hbc56Interrupt(tmsDevice->irq, INTERRUPT_RELEASE);
return 1;
}
else if (addr == tmsDevice->dataAddr)
{
if (dbg)
{
*val = vrEmuTms9918ReadDataNoInc(tmsDevice->tms9918);
}
else
{
*val = vrEmuTms9918ReadData(tmsDevice->tms9918);
}
return 1;
}
}
return 0;
}
/* Function: writeTms9918Device
* --------------------
* write to the tms. address determines address/register or data
*/
static uint8_t writeTms9918Device(HBC56Device* device, uint16_t addr, uint8_t val)
{
TMS9918Device* tmsDevice = getTms9918Device(device);
if (tmsDevice)
{
if (addr == tmsDevice->regAddr)
{
vrEmuTms9918WriteAddr(tmsDevice->tms9918, val);
return 1;
}
else if (addr == tmsDevice->dataAddr)
{
vrEmuTms9918WriteData(tmsDevice->tms9918, val);
return 1;
}
}
return 0;
}
/* Function: readTms9918Vram
* --------------------
* read a value from vram directly
*/
uint8_t readTms9918Vram(HBC56Device* device, uint16_t vramAddr)
{
TMS9918Device* tmsDevice = getTms9918Device(device);
if (tmsDevice)
{
return vrEmuTms9918VramValue(tmsDevice->tms9918, vramAddr);
}
return 0;
}
/* Function: readTms9918Reg
* --------------------
* read a registry value directly
*/
uint8_t readTms9918Reg(HBC56Device* device, uint8_t reg)
{
TMS9918Device* tmsDevice = getTms9918Device(device);
if (tmsDevice)
{
return vrEmuTms9918RegValue(tmsDevice->tms9918, reg);
}
return 0;
}
/* Function: writeTms9918Reg
* --------------------
* write a regiter value directly to the tms9918
*/
void writeTms9918Reg(HBC56Device* device, uint8_t reg, uint8_t value)
{
TMS9918Device* tmsDevice = getTms9918Device(device);
if (tmsDevice)
{
vrEmuTms9918WriteRegValue(tmsDevice->tms9918, reg, value);
}
}
/* Function: vrEmuTms9918DisplayMode
* --------------------
* current display mode
*/
int getTms9918Mode(HBC56Device* device)
{
TMS9918Device* tmsDevice = getTms9918Device(device);
if (tmsDevice)
{
return vrEmuTms9918DisplayMode(tmsDevice->tms9918);
}
return 0;
}