apple1-videocard-lib/lib/tms9918.h
2021-12-17 10:23:18 +01:00

171 lines
5.4 KiB
C

// TODO a bitmapped text writing routine (double size ecc)
// TODO console like text output in screen 2
// TODO more fonts (C64 and PET/VIC20)
// TODO how to switch fonts?
// TODO do fonts need to start from 32 or 0?
// TODO sprite routines
// TODO test the interrupt routines
// TODO finalize hexdump.js and update README.md
// TODO allow redefinition of I/O ports
// TODO wait_end_of_frame()
// TODO screen1() and screen2() helpers
#pragma encoding(ascii) // encode strings in plain ascii
#include "utils.h"
#ifdef APPLE1
const byte *VDP_DATA = 0xCC00; // TMS9918 data port (VRAM)
const byte *VDP_REG = 0xCC01; // TMS9918 register port (write) or status (read)
#else
const byte *VDP_DATA = 0xA000; // TMS9918 data port (VRAM)
const byte *VDP_REG = 0xA001; // TMS9918 register port (write) or status (read)
#endif
// control port bits
const byte WRITE_TO_VRAM = 0b01000000; // write to VRAM command
const byte READ_FROM_VRAM = 0b00000000; // read from VRAM command
const byte HIADDRESS_MASK = 0b00111111; // bit mask for the high byte of the address
const byte WRITE_TO_REG = 0b10000000; // write to register command
const byte REGNUM_MASK = 0b00000111; // bit mask for register number (0-7)
// register 0 masks
const byte REG0_M3_MASK = 0b00000010;
const byte REG0_EXTVID_MASK = 0b00000001;
// register 1 masks
const byte REG1_16K_MASK = 0b10000000;
const byte REG1_BLANK_MASK = 0b01000000;
const byte REG1_IE_MASK = 0b00100000;
const byte REG1_M1M2_MASK = 0b00011000;
const byte REG1_UNUSED_MASK = 0b00000100;
const byte REG1_SIZE_MASK = 0b00000010;
const byte REG1_MAG_MASK = 0b00000001;
// TMS9918 color palette
const byte COLOR_TRANSPARENT = 0x0;
const byte COLOR_BLACK = 0x1;
const byte COLOR_MEDIUM_GREEN = 0x2;
const byte COLOR_LIGHT_GREEN = 0x3;
const byte COLOR_DARK_BLUE = 0x4;
const byte COLOR_LIGHT_BLUE = 0x5;
const byte COLOR_DARK_RED = 0x6;
const byte COLOR_CYAN = 0x7;
const byte COLOR_MEDIUM_RED = 0x8;
const byte COLOR_LIGHT_RED = 0x9;
const byte COLOR_DARK_YELLOW = 0xA;
const byte COLOR_LIGHT_YELLOW = 0xB;
const byte COLOR_DARK_GREEN = 0xC;
const byte COLOR_MAGENTA = 0xD;
const byte COLOR_GREY = 0xE;
const byte COLOR_WHITE = 0xF;
// The library has a fixed VRAM memory layout valid for SCREEN 1 and 2
//
// pattern table: $0000-$17FF (256*8*3)
// sprite patterns: $1800-$19FF
// color table: $2000-$27FF (256*8*3)
// name table: $3800-$3AFF (32*24 = 256*3 = 768)
// sprite attributes: $3B00-$3BFF
// unused $3C00-$3FFF
//
const word TMS_NAME_TABLE = 0x3800;
const word TMS_COLOR_TABLE = 0x2000;
const word TMS_PATTERN_TABLE = 0x0000;
const word TMS_SPRITE_ATTRS = 0x3b00;
const word TMS_SPRITE_PATTERNS = 0x1800;
// macro for combining foreground and background into a single byte value
#define FG_BG(f,b) (((f)<<4)|(b))
// status register bits (read only)
#define FRAME_BIT(a) ((a) & 0b10000000)
#define FIVESPR_BIT(a) ((a) & 0b01000000)
#define COLLISION_BIT(a) ((a) & 0b00100000)
#define SPRITE_NUM(a) ((a) & 0b00011111)
// read/write to TMS9918 macros
#define TMS_WRITE_CTRL_PORT(a) (*VDP_REG=(byte)(a))
#define TMS_WRITE_DATA_PORT(a) (*VDP_DATA=(byte)(a))
#define TMS_READ_CTRL_PORT (*VDP_REG)
#define TMS_READ_DATA_PORT (*VDP_DATA)
// buffer containing the last register values, because TMS registers are write only
byte tms_regs_latch[8];
// cursor coordinates for the console functions
byte tms_cursor_x;
byte tms_cursor_y;
byte tms_reverse;
// sets the VRAM address on the TMS9918 for a write operation
void tms_set_vram_write_addr(word addr) {
TMS_WRITE_CTRL_PORT(LOBYTE(addr));
TMS_WRITE_CTRL_PORT((HIBYTE(addr) & HIADDRESS_MASK)|WRITE_TO_VRAM);
}
// sets the VRAM address on the TMS9918 for a read operation
void tms_set_vram_read_addr(word addr) {
TMS_WRITE_CTRL_PORT(LOBYTE(addr));
TMS_WRITE_CTRL_PORT((HIBYTE(addr) & HIADDRESS_MASK)|READ_FROM_VRAM);
}
// writes a value to a TMS9918 register (0-7)
void tms_write_reg(byte regnum, byte val) {
TMS_WRITE_CTRL_PORT(val);
TMS_WRITE_CTRL_PORT((regnum & REGNUM_MASK)|WRITE_TO_REG);
tms_regs_latch[regnum] = val; // save value to buffer
}
// sets border color and background for mode 0
inline void tms_set_color(byte col) {
tms_write_reg(7, col);
}
// initialize all registers from a table
void tms_init_regs(byte *table) {
for(byte i=0;i<8;i++) {
tms_write_reg(i, table[i]);
}
}
const byte INTERRUPT_ENABLED = 1;
const byte INTERRUPT_DISABLED = 0;
// sets the interrupt enable bit on register 1
void tms_set_interrupt_bit(byte val) {
byte regvalue = tms_regs_latch[1] & (~REG1_IE_MASK);
if(val) regvalue |= REG1_IE_MASK;
tms_write_reg(1, regvalue);
}
const byte BLANK_ON = 0;
const byte BLANK_OFF = 1;
// sets the blank bit on register 1
void tms_set_blank(byte val) {
byte regvalue = tms_regs_latch[1] & (~REG1_BLANK_MASK);
if(val) regvalue |= REG1_BLANK_MASK;
tms_write_reg(1, regvalue);
}
// sets the external video input bit on register 0
void tms_set_external_video(byte val) {
byte regvalue = tms_regs_latch[0] & (~REG0_EXTVID_MASK);
if(val) regvalue |= REG0_EXTVID_MASK;
tms_write_reg(0, regvalue);
}
inline void tms_wait_end_of_frame() {
while(!FRAME_BIT(TMS_READ_CTRL_PORT));
}
#include "apple1.h"
#include "font8x8.h"
#include "sprites.h"
#include "screen1.h"
#include "screen2.h"
#include "interrupt.h"