Amstrad CPC, CRTC Address Generator

crtc.c

#include <stdio.h>

typedef unsigned char u8;
typedef unsigned short u16;
typedef unsigned int u32;

#define VIDEO_ADDR(MA, RA) \
    ((MA & 0x3FF) << 1) | ((RA & 7) << 11) | ((MA & 0x3000) << 2)

#define PRINT_CHAR_ADDR

int main()
{
    u8 R13;
    u8 R12;
    u8 R0;
    u8 R9;
    u8 R1;
    u8 R6;
    int clock;

    R1 = 0x28;
    R9 = 0x7;
    R0 = 0x3F;
    R12 = 0x30;
    R13 = 0;
    R6 = 25;
    int refresh_addr = (u16) R13 | (((u16) R12 << 8));

    clock = 0;

    while (1) {
        u16 MA; /* MA pins on CRTC */
        u16 RA;  /* Raster pins on CRTC */
        int line;

        line = clock / ((R9 + 1) * (R0 + 1));

        MA = refresh_addr + (line * R1 + (clock % (R0 + 1)));
        RA = (clock / (R0 + 1)) % (R9 + 1);

        if (line >= R6) {
            break;
        }

#ifdef PRINT_ALL_ADDR
        printf("%.4x", VIDEO_ADDR(MA, RA));
#endif

#ifdef PRINT_CHAR_ADDR
        if (clock % (R0 + 1) == 0) {
            static int c = 0;

            if (c % (R9 + 1) == 0) {
                printf("\n");
                printf("%2d:   ", (line + 1));
            }

            printf("%.4x", VIDEO_ADDR(MA, RA));

            if ((c + 1) % (R9 + 1) != 0) {
                printf(", ");
            }

            c += 1;
        }
#endif

        clock += 1;
    }
    
    return 0;
}

 1:   c000, c800, d000, d800, e000, e800, f000, f800
 2:   c050, c850, d050, d850, e050, e850, f050, f850
 3:   c0a0, c8a0, d0a0, d8a0, e0a0, e8a0, f0a0, f8a0
 4:   c0f0, c8f0, d0f0, d8f0, e0f0, e8f0, f0f0, f8f0
 5:   c140, c940, d140, d940, e140, e940, f140, f940
 6:   c190, c990, d190, d990, e190, e990, f190, f990
 7:   c1e0, c9e0, d1e0, d9e0, e1e0, e9e0, f1e0, f9e0
 8:   c230, ca30, d230, da30, e230, ea30, f230, fa30
 9:   c280, ca80, d280, da80, e280, ea80, f280, fa80
10:   c2d0, cad0, d2d0, dad0, e2d0, ead0, f2d0, fad0
11:   c320, cb20, d320, db20, e320, eb20, f320, fb20
12:   c370, cb70, d370, db70, e370, eb70, f370, fb70
13:   c3c0, cbc0, d3c0, dbc0, e3c0, ebc0, f3c0, fbc0
14:   c410, cc10, d410, dc10, e410, ec10, f410, fc10
15:   c460, cc60, d460, dc60, e460, ec60, f460, fc60
16:   c4b0, ccb0, d4b0, dcb0, e4b0, ecb0, f4b0, fcb0
17:   c500, cd00, d500, dd00, e500, ed00, f500, fd00
18:   c550, cd50, d550, dd50, e550, ed50, f550, fd50
19:   c5a0, cda0, d5a0, dda0, e5a0, eda0, f5a0, fda0
20:   c5f0, cdf0, d5f0, ddf0, e5f0, edf0, f5f0, fdf0
21:   c640, ce40, d640, de40, e640, ee40, f640, fe40
22:   c690, ce90, d690, de90, e690, ee90, f690, fe90
23:   c6e0, cee0, d6e0, dee0, e6e0, eee0, f6e0, fee0
24:   c730, cf30, d730, df30, e730, ef30, f730, ff30
25:   c780, cf80, d780, df80, e780, ef80, f780, ff80