Colours on a Microbee - Printable Version

Code:

crtc    equ    0ch    ;6545 control port

crtd    equ    0dh    ;6545 data port





;set up the 64*16 screen format 

init64:

    ld    hl,d6545

    ld    b,16

lp6545:    

        ld    a,b

    dec    a

    out    (crtc),a

    ld    a,(hl)

    out    (crtd),a

    dec    hl

    djnz    lp6545

    ret



;--------------------------------------------------------------------------

;6545 (Video Driver Chip) DATA (data to set the 6545 to 64*16 screen format

;--------------------------------------------------------------------------

    db    108-1    ;horizontal sync timing constant

    db    64            ;number of displayed characters per line

    db    81            ;horizontal sync position

    db    55            ;horizontal and vertical sync width

    db    19-1            ;vertical sync width

    db    09            ;vertical sync timing constant

    db    16            ;number of displayed rows per screen

    db    17            ;vertical sync position

    db    72            ;mode control constant

    db    16-1            ;number of scan lines per character

    db    20h+15    ;cursor mode and start line

    db    15            ;cursor end line

    dw    0            ;display start address relative to 0F000h

    db    0            ;cursor position

d6545:    

        db    0

Code:

enum {

    crtStatusVSync = 5,                // Video is in vsync

    crtStatusLightPen,                 // Keyboard hit

    crtStatusUpdateReady,              // Wrote to reg 31

};



#define VDU_VSYNC_MASK ( 1 << crtStatusVSync )



static volatile __sfr __at 0x0C CrtRegPort;

static volatile __sfr __at 0x0D CrtDataPort;

static volatile __sfr __at 0x08 VduBankPort;



// from the R6545 crt display controller manual

enum {



    crtHorizontalTotalChars = 0,

    crtHorizontalDisplayedChars = 1,

    crtHorizontalSyncPosition = 2,



    crtHorizontalVerticalSyncWidths = 3,



    crtVerticalTotalRows = 4,

    crtVerticalTotalLineAdjust = 5,

    crtVerticalDisplayedRows = 6,

    crtVerticalSyncPosition = 7,

    crtModeControl = 8,

    crtRowScanLines = 9,



    crtCursorPositionHigh = 14,

    crtCursorPositionLow,

};



///< Setup crt to 64x16 tiles and hide the cursor

void vdu_crt_setup() {



    // Cursor off screen

    CrtRegPort = crtCursorPositionHigh;

    CrtDataPort = 0xff;

    CrtRegPort = crtCursorPositionLow;

    CrtDataPort = 0xff;



    CrtRegPort = crtHorizontalDisplayedChars; // Columns on screen

    CrtDataPort = 64;

    CrtRegPort = crtVerticalDisplayedRows;    // Rows on screen

    CrtDataPort = 16;

    CrtRegPort = crtRowScanLines;             // Rows per character - cuts of the bottom of tiles

    CrtDataPort = 15;                         // Rows - 1

}



///< Switch in vdu PCG or colour data at 0xF8000

void vdu_bank( bool colour ) __fastcall {



    VduBankPort = colour ? 0x47 : 0x07;

}



///< Wait for full vblank cycle, so 1/50th of a second has passed (for timing)

void vdu_wait() {



    #define VDU_STATUS_PORT 0x0C

    #define VDU_VSYNC_BIT 5



    __asm



crt_poll:

        in      a,(#VDU_STATUS_PORT)

        bit    #VDU_VSYNC_BIT,a

        jp      z, crt_poll



crt_poll_end:

        in      a,(#VDU_STATUS_PORT)

        bit    #VDU_VSYNC_BIT,a

        jp      nz, crt_poll_end



    __endasm;



}