Re: Programming the Sprite Card (was NES - Apple Sprite card)

[mjmahon@aol.com (Michael J. Mahon)]

In article <3E765D17.6040103@noneofyourbusiness.com>, Exegete
<millers@noneofyourbusiness.com> writes:
>
>Yves McDonald wrote:
>> The story so far with my attemps to program the Sprite Card:
>> 
>> I'm able to program it using Orca/Pascal with various pointer tricks. I 
>> have learned how to use the GS Toolbox to display hex values on screen 
>> for debug purpose.  After a three months break,  I had time to wire an 
>> RCA plug to it and get a display on an ordinary TV set (no RF 
>> modulator).  First disappointment,  I only get black and white pictures 
>> but I'm satisfied to see that old set of chips to actually work and 
>> respond to wathever data I write in registers or in the VRAM.
>> 
>> I don't know why I don't get any colors.  Perhaps I have an impedance 
>> mismatch between TV input and card output or a defect in the Card's 
>> video signal buffer amplifier (a pair of transistors - basically).  Any 
>> suggesstions about lack of colors?
>> 
>> Meanwhile, I'll write a set of VDP init and VRAM access routines to make 
>> sprite/backdrop creation a little easier.
>> 
>> Yves
>> 
>> Michael J. Mahon worte
>> 
>>> Yves McDonald wrote:
>>>
>>>
>>>> I think the paper about the sprite card was published in Byte issue 
>>>> on LOGO language (circa 1982).
>>>>
>>>> There are code samples in TI 9900 assembly language in TI books 
>>>> indeed.   From the chip count on the sprite card, the 9918A 
>>>> interfaces nicely to the Apple bus.
>>>
>>>
>>>
>>> Yes, it interfaces very easily, though the actual decoding on this card
>>> is somewhat peculiar.
>>>
>>> The card also contains a 2516 EPROM which contains 6502 firmware
>>> used by Sprite Logo to control the card.  I glanced at it, but have not
>>> done much disassembly.
>>>
>>> The TMS9918A was also used in the MSX computers, and that is a
>>> good place to go for more information on the chip:
>>>
>>> http://www.msxnet.org/tech/
>>>
>>> After seeing how reticulated the 9918 is to control, I admit that my
>>> interest flagged somewhat.  But that can be remedied by writing a
>>> set of low-level drivers to provide a more "natural" programming
>>> interface.
>>>
>>> I'd be very interested in any software that used this card.
>
>Are there any chips that would make it difficult to impossible to create 
>more cards like this one? Other than the 9918a itself?

That's pretty much it--the DRAM and clue logic is pretty generic.

-michael

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