VGA driver tile and color retrieval refactor about jcap HOT 3 CLOSED

line    rdbyte          ti,     tmptr           ' Read tile index of current map tile
        add             tmptr,  #1              ' Increment tile map pointer to color index
        shl             ti,     tOffset         ' Multiply tile index by size of tile map
        rdbyte          ci,     tmptr           ' Store color index of current map tile
        add             ti,     tpbase          ' Increment tile index to correct line
        add             ti,     tpptr           ' Add tile palette pointer to tile index to specify row of tile to be displayed
rdtile
movp    rdlong          0-0,    ti              ' Read 16-pixel-wide tile from Main RAM
        shl             ci,     #2              ' Multiply color index by size of color palette
        add             ci,     cpbase          ' Increment color index to correct palette
movc    rdlong          0-0,    ci              ' Read tile from Main RAM
        add             movp,   incDest         ' Increment tile buffer pointer
        add             movc,   incDest         ' Increment color buffer pointer
        add             tmptr,  #1              ' Increment tile map pointer to next tile in row
        djnz            tptr,   #line           ' Generate one scanline of data