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emul/z80: extract tms9918 unit from sms_vdp

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I'm planning on supporting Text Mode soon, and SMS' VDP, when mode
4 is not active, behaves mostly like a regular TMS9918.

By having this behavior in a separate unit, we'll be able to use it
in other systems.
This commit is contained in:
Virgil Dupras 2020-11-12 11:13:18 -05:00
parent c7d8de25b2
commit 09c01c4a43
6 changed files with 116 additions and 54 deletions
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3
emul/z80/Makefile
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@ -1,7 +1,8 @@
TARGETS = forth rc2014 sms ti84
OBJS = emul.o z80.o
RC2014_OBJS = $(OBJS) sio.o acia.o sdc.o rc2014_spi.o
SMS_OBJS = $(OBJS) sms_vdp.o sms_ports.o sms_pad.o ps2_kbd.o sdc.o sms_spi.o
SMS_OBJS = $(OBJS) tms9918.o sms_vdp.o sms_ports.o sms_pad.o ps2_kbd.o sdc.o \
sms_spi.o
TI84_OBJS = $(OBJS) t6a04.o ti84_kbd.o
CDIR = ../../cvm
STAGE = $(CDIR)/stage

2
emul/z80/sms.c
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@ -48,7 +48,7 @@ static SPI spi;
static uint8_t iord_vdp_cmd()
{
return vdp_cmd_rd(&vdp);
return tms_cmd_rd(&vdp.tms);
}
static uint8_t iord_vdp_data()

69
emul/z80/sms_vdp.c
View File

@ -3,55 +3,47 @@
void vdp_init(VDP *vdp)
{
memset(vdp->vram, 0, VDP_VRAM_SIZE);
memset(vdp->regs, 0, 0x10);
vdp->has_cmdlsb = false;
vdp->curaddr = 0;
}
uint8_t vdp_cmd_rd(VDP *vdp)
{
return 0;
tms_init(&vdp->tms);
memset(vdp->cram, 0, VDP_CRAM_SIZE);
}
void vdp_cmd_wr(VDP *vdp, uint8_t val)
{
if (!vdp->has_cmdlsb) {
vdp->cmdlsb = val;
vdp->has_cmdlsb = true;
return;
}
vdp->has_cmdlsb = false;
if ((val & 0xc0) == 0x80) {
// set register
vdp->regs[val&0xf] = vdp->cmdlsb;
} else if ((val & 0xc0) == 0xc0) {
// palette RAM
vdp->curaddr = 0x4000 + (vdp->cmdlsb&0x1f);
if (!vdp->tms.has_cmdlsb) {
tms_cmd_wr(&vdp->tms, val);
} else {
// VRAM
vdp->curaddr = ((val&0x3f) << 8) + vdp->cmdlsb;
if ((val & 0xc0) == 0xc0) {
// palette RAM
// curaddr > VRAM == addr in CRAM
vdp->tms.curaddr = TMS_VRAM_SIZE + (vdp->tms.cmdlsb&0x1f);
} else {
tms_cmd_wr(&vdp->tms, val);
}
}
}
uint8_t vdp_data_rd(VDP *vdp)
{
uint8_t res = vdp->vram[vdp->curaddr];
if (vdp->curaddr < VDP_VRAM_SIZE) {
vdp->curaddr++;
TMS9918 *tms = &vdp->tms;
if (tms->curaddr < TMS_VRAM_SIZE) {
return tms_data_rd(&vdp->tms);
} else if (tms->curaddr - TMS_VRAM_SIZE < VDP_CRAM_SIZE) {
return vdp->cram[tms->curaddr++-TMS_VRAM_SIZE];
} else {
return 0;
}
return res;
}
void vdp_data_wr(VDP *vdp, uint8_t val)
{
vdp->vram[vdp->curaddr] = val;
if (vdp->curaddr < VDP_VRAM_SIZE) {
vdp->curaddr++;
TMS9918 *tms = &vdp->tms;
if (tms->curaddr < TMS_VRAM_SIZE) {
tms_data_wr(&vdp->tms, val);
} else if (tms->curaddr - TMS_VRAM_SIZE < VDP_CRAM_SIZE) {
vdp->cram[tms->curaddr++-TMS_VRAM_SIZE] = val;
}
}
// Returns a 8-bit RGB value (0b00bbggrr)
uint8_t vdp_pixel(VDP *vdp, uint16_t x, uint16_t y)
{
if (x >= VDP_SCREENW) {
@ -60,10 +52,11 @@ uint8_t vdp_pixel(VDP *vdp, uint16_t x, uint16_t y)
if (y >= VDP_SCREENH) {
return 0;
}
TMS9918 *tms = &vdp->tms;
// name table offset
uint16_t offset = (vdp->regs[2] & 0xe) << 10;
uint16_t offset = (tms->regs[2] & 0xe) << 10;
offset += ((y/8) << 6) + ((x/8) << 1);
uint16_t tableval = vdp->vram[offset] + (vdp->vram[offset+1] << 8);
uint16_t tableval = tms->vram[offset] + (tms->vram[offset+1] << 8);
uint16_t tilenum = tableval & 0x1ff;
// is palette select bit on? if yes, use sprite palette instead
uint8_t palettemod = tableval & 0x800 ? 0x10 : 0;
@ -74,10 +67,10 @@ uint8_t vdp_pixel(VDP *vdp, uint16_t x, uint16_t y)
uint8_t bitnum = 7 - (x%8);
// Now, let's compose the result by pushing the right bit of our 4 bytes
// into our result.
uint8_t palette_id = ((vdp->vram[offset] >> bitnum) & 1) + \
(((vdp->vram[offset+1] >> bitnum) & 1) << 1) + \
(((vdp->vram[offset+2] >> bitnum) & 1) << 2) + \
(((vdp->vram[offset+3] >> bitnum) & 1) << 3);
uint8_t rgb = vdp->vram[0x4000+palettemod+palette_id];
uint8_t palette_id = ((tms->vram[offset] >> bitnum) & 1) + \
(((tms->vram[offset+1] >> bitnum) & 1) << 1) + \
(((tms->vram[offset+2] >> bitnum) & 1) << 2) + \
(((tms->vram[offset+3] >> bitnum) & 1) << 3);
uint8_t rgb = vdp->cram[palettemod+palette_id];
return rgb;
}

18
emul/z80/sms_vdp.h
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@ -1,26 +1,16 @@
#include <stdint.h>
#include <stdbool.h>
#include "tms9918.h"
#define VDP_VRAM_SIZE 0x4020
#define VDP_CRAM_SIZE 0x20
#define VDP_SCREENW (32*8)
#define VDP_SCREENH (24*8)
// Offset of the name table
#define VDP_NTABLE_OFFSET 0x3800
typedef struct {
// the last 0x20 is palette RAM
uint8_t vram[VDP_VRAM_SIZE];
uint8_t regs[0x10];
uint8_t cmdlsb;
bool has_cmdlsb;
uint16_t curaddr;
TMS9918 tms;
uint8_t cram[VDP_CRAM_SIZE];
} VDP;
void vdp_init(VDP *vdp);
uint8_t vdp_cmd_rd(VDP *vdp);
void vdp_cmd_wr(VDP *vdp, uint8_t val);
uint8_t vdp_data_rd(VDP *vdp);
void vdp_data_wr(VDP *vdp, uint8_t val);
// result is a RGB value
uint8_t vdp_pixel(VDP *vdp, uint16_t x, uint16_t y);

54
emul/z80/tms9918.c Normal file
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@ -0,0 +1,54 @@
#include <string.h>
#include "tms9918.h"
void tms_init(TMS9918 *tms)
{
memset(tms->vram, 0, TMS_VRAM_SIZE);
memset(tms->regs, 0, 0x10);
tms->has_cmdlsb = false;
tms->curaddr = 0;
}
uint8_t tms_cmd_rd(TMS9918 *tms)
{
return 0;
}
void tms_cmd_wr(TMS9918 *tms, uint8_t val)
{
if (!tms->has_cmdlsb) {
tms->cmdlsb = val;
tms->has_cmdlsb = true;
return;
}
tms->has_cmdlsb = false;
if ((val & 0xc0) == 0x80) {
// set register
tms->regs[val&0xf] = tms->cmdlsb;
} else {
// VRAM
tms->curaddr = ((val&0x3f) << 8) + tms->cmdlsb;
}
}
uint8_t tms_data_rd(TMS9918 *tms)
{
if (tms->curaddr < TMS_VRAM_SIZE) {
return tms->vram[tms->curaddr++];
} else {
return 0;
}
}
void tms_data_wr(TMS9918 *tms, uint8_t val)
{
if (tms->curaddr < TMS_VRAM_SIZE) {
tms->vram[tms->curaddr++] = val;
}
}
// Returns a 8-bit RGB value (0b00bbggrr)
uint8_t tms_pixel(TMS9918 *tms, uint16_t x, uint16_t y)
{
return 0; // no TMS9918 mode implemented yet
}

24
emul/z80/tms9918.h Normal file
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@ -0,0 +1,24 @@
#pragma once
#include <stdint.h>
#include <stdbool.h>
#define TMS_VRAM_SIZE 0x4000
// Offset of the name table
#define TMS_NTABLE_OFFSET 0x3800
typedef struct {
uint8_t vram[TMS_VRAM_SIZE];
uint8_t regs[0x10];
uint8_t cmdlsb;
bool has_cmdlsb;
uint16_t curaddr;
} TMS9918;
void tms_init(TMS9918 *tms);
uint8_t tms_cmd_rd(TMS9918 *tms);
void tms_cmd_wr(TMS9918 *tms, uint8_t val);
uint8_t tms_data_rd(TMS9918 *tms);
void tms_data_wr(TMS9918 *tms, uint8_t val);
// result is a RGB value
uint8_t tms_pixel(TMS9918 *tms, uint16_t x, uint16_t y);