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Code: Select all

#include <system.h>
#include <inline.h>

#define COLUMNS 80
#define ROWS 25
#define VIDEO_ADDR 0xB8000

/* @iport - index port, @iport + 1 - data port */
static inline void vga_write_reg(u16_t iport, byte_t reg, byte_t val){
	to_port_b(iport, reg); /* Select register */
	to_port_b(iport + 1, val); /* Do writing through data port */
}
/* @iport - index port, @iport + 1 - data port */
static inline byte_t vga_read_reg(u16_t iport, byte_t reg){
	to_port_b(iport, reg); /* Select register */
	return from_port_b(iport + 1); /* Do reading through data port */
}

#define VGA_SEQ_INDEX_PORT 0x3C4
#define VGA_SEQ_DATA_PORT 0x3C5

#define VGA_GC_INDEX_PORT 0x3CE
#define VGA_GC_DATA_PORT 0x3CF

#define VGA_CRTC_INDEX_PORT 0x3D4
#define VGA_CRTC_DATA_PORT 0x3D5

#define VGA_SEQ_MAP_MASK_REG 0x02
#define VGA_SEQ_CHARSET_REG 0x03
#define VGA_SEQ_MEMORY_MODE_REG 0x04

#define VGA_GC_READ_MAP_SELECT_REG 0x04
#define VGA_GC_GRAPHICS_MODE_REG 0x05
#define VGA_GC_MISC_REG 0x06

#define BYTES_PER_GLYPTH 16
#define BYTES_SKIP 16
#define CHARSET_LENGTH 256
#define FONT_SIZE CHARSET_LENGTH * BYTES_PER_GLYPTH

static void set_font(unsigned char font[FONT_SIZE]){
	int i, j;
	unsigned char *p = (unsigned char *)0xB8000;
	byte_t mem_mode, graphics_mode;
	
	/* Panel 2 write enable */
	vga_write_reg(VGA_SEQ_INDEX_PORT, VGA_SEQ_MAP_MASK_REG, 0x04);
	
	/* To be shure, that the first font in the plane 2 is selected */
	vga_write_reg(VGA_SEQ_INDEX_PORT, VGA_SEQ_CHARSET_REG, 0x00);
	
	mem_mode = vga_read_reg(VGA_SEQ_INDEX_PORT, VGA_SEQ_MEMORY_MODE_REG);
	vga_write_reg(VGA_SEQ_INDEX_PORT, VGA_SEQ_MEMORY_MODE_REG, 0x06);
	
        /* I think this line is unnecessary */
	vga_write_reg(VGA_GC_INDEX_PORT, VGA_GC_READ_MAP_SELECT_REG, 0x02);
	
	graphics_mode = vga_read_reg(VGA_GC_INDEX_PORT, VGA_GC_GRAPHICS_MODE_REG);
	vga_write_reg(VGA_GC_INDEX_PORT, VGA_GC_GRAPHICS_MODE_REG, 0x00);
	
        /* And this line is unnecessary too, since I now, that address is 0xB8000 */
	vga_write_reg(VGA_GC_INDEX_PORT, VGA_GC_MISC_REG, 0x0C);
	
	/* Write charmap */
	for(i = 0; i < CHARSET_LENGTH; i++){
		for(j = 0; j < BYTES_PER_GLYPTH; j++){
			*p = *font;
			++p;
			++font;
		}
		p += BYTES_SKIP;
	}
	
	/* Restore VGA to normal operation */
	
	/* Panels 0 and 1 write enable */
	vga_write_reg(VGA_SEQ_INDEX_PORT, VGA_SEQ_MAP_MASK_REG, 0x03);
	vga_write_reg(VGA_SEQ_INDEX_PORT, VGA_SEQ_MEMORY_MODE_REG, mem_mode);
	
	vga_write_reg(VGA_GC_INDEX_PORT, VGA_GC_READ_MAP_SELECT_REG, 0x00);
	vga_write_reg(VGA_GC_INDEX_PORT, VGA_GC_GRAPHICS_MODE_REG, graphics_mode);
	vga_write_reg(VGA_GC_INDEX_PORT, VGA_GC_MISC_REG, 0x0C);
}

Code: Select all

        MOV AX, 0xB800
        MOV ES, AX

        MOV DX, 0x3C4
        MOV AX, 0x0402          ; seq.mapmask = !0, !1, 2, !3
        OUT DX, AX
        MOV AX, 0x0003          ; seq.font A=0 B=0
        OUT DX, AX
        MOV AX, 0x0604          ; seq.memmode = O/E off, chain4 off, ext on
        OUT DX, AX

        MOV DX, 0x3CE
        MOV AX, 0x0005          ; gx.modereg = !256, !shift, !OE, writemode_0
        OUT DX, AX
        MOV AX, 0x0C06          ; gx.miscreg = map_b8000, !HostOE, !graphics
        OUT DX, AX

        ; set font to garbage
        MOV CX, 0x1000
        XOR DI, DI
.loop:  MOV AL, CL
        MOV [ES:DI], CL
        INC DI
        DEC CX 

Code: Select all

puts("Old font:\n");
for(i = 0; i < 256; i++)
putchar(i);
set_font(my_font);
puts("\nNew font:\n");
for(i = 0; i < 256; i++)
putchar(i);