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Enumerate CGA CRTC registers and modes and implement that into the code

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starfrost013
2025-06-09 14:12:13 +01:00
parent 79c408b286
commit b639bf1853
2 changed files with 107 additions and 64 deletions
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36
src/include/86box/vid_cga.h
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@@ -15,11 +15,47 @@
*
* Copyright 2008-2018 Sarah Walker.
* Copyright 2016-2018 Miran Grca.
* Copyright 2025 starfrost (refactoring)
*/
#ifndef VIDEO_CGA_H
#define VIDEO_CGA_H
// Mode flags for the CGA.
// Set by writing to 3D8
typedef enum cga_mode_flags_e
{
CGA_MODE_FLAG_HIGHRES = 1 << 0, // 80-column text mode
CGA_MODE_FLAG_GRAPHICS = 1 << 1, // Graphics mode
CGA_MODE_FLAG_BW = 1 << 2, // Black and white
CGA_MODE_FLAG_VIDEO_ENABLE = 1 << 3, // 0 = no video (as if the video was 0)
CGA_MODE_FLAG_HIGHRES_GRAPHICS = 1 << 4, // 640*200 mode. Corrupts the
CGA_MODE_FLAG_BLINK = 1 << 5, // If this is set, bit 5 of textmode characters blinks. Otherwise it is a high-intensity bg mode.
} cga_mode_flags;
// Motorola MC6845 CRTC registers
typedef enum cga_crtc_registers_e
{
CGA_CRTC_HTOTAL = 0x0, // Horizontal total (total number of characters incl. hsync)
CGA_CRTC_HDISP = 0x1, // Horizontal display
CGA_CRTC_HSYNC_POS = 0x2, // Horizontal position of horizontal ysnc
CGA_CRTC_HSYNC_WIDTH = 0x3, // Width of horizontal sync
CGA_CRTC_VTOTAL = 0x4, // Vertical total (total number of scanlines incl. vsync)
CGA_CRTC_VTOTAL_ADJUST = 0x5, // Vertical total adjust value
CGA_CRTC_VDISP = 0x6, // Vertical display (total number of displayed scanline)
CGA_CRTC_VSYNC = 0x7, // Vertical sync scanline number
CGA_CRTC_INTERLACE = 0x8, // If set, interlacing mode is enabled
CGA_CRTC_MAX_SCANLINE_ADDR = 0x9,
CGA_CRTC_CURSOR_START = 0xA,
CGA_CRTC_CURSOR_END = 0xB,
CGA_CRTC_START_ADDR_HIGH = 0xC,
CGA_CRTC_START_ADDR_LOW = 0xD,
CGA_CRTC_CURSOR_ADDR_HIGH = 0xE,
CGA_CRTC_CURSOR_ADDR_LOW = 0xF,
CGA_CRTC_LIGHT_PEN_ADDR_HIGH = 0x10,
CGA_CRTC_LIGHT_PEN_ADDR_LOW = 0x11,
} cga_crtc_registers;
typedef struct cga_t {
mem_mapping_t mapping;