Personally I never use tiles, I'd rather output the pixels myself. This gives you full control of the display. Take a look at the zrt80 driver in MESS. This shows the basic concept for outputting lines of dots on the screen. You will need to change the 'for' loop to pick up every 4th byte ( change x++ to x+=4 ).
Notice where 8 pixels are output, bits 7 to 0, left to right. Since your character generator has a different order, put the order here. This saves you the overhead of doing BITSWAP8.
Once you have text on the screen, then you can start thinking about implementing the attributes.
> hello ,
>
> this is my first try on the MAME emulator project.
> Board info :
> CPU : MC68000 8mhz
> Video : MC6845
> Audio : AY3-8912
>
> I have done for the moment :
> 1. mapping of the board
> 2. skeleton of the driver (software run, but still some i/o todo)
> 3. dump of ROM ,NVRAM, emulation of PAL
>
> currently , I am lost in the decoding of the video section
> VIDEO RAM work with 2 BYTES
> 1 ATTRIBUTE BYTE (color + bank select)
> 1 TILE BYTE
>
> there is a BYTESWAP at the output of ROM GFX plus
> a funny use of clock in the RASTER ROW.
>
> I have attached a DUMP of the videoram and the schematic
> if someone can help me.
>
> thanks
>
> Yves
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video tilemap problem
