Any BIT3 Video card users/experts here?

[candle]

Joe, look at the block diagrams in pdf You found, and functional description

it is written, that chip loads character row (when LD/SH signal is high) to shift out during shift phase (when LD/SH is low)

now compare this to 74LS165 chip

it has SH/LD signal (pin #2 of crt8021), Clock singal (pin #3), A-H inputs (A0 to A7 - pin #4 to 11), and Output H (pin #1)

its very simple chip that can be synthetised inside of small cpld device like xc9536 or xc9572

 

it can be fun if You would like to spend some time reverse engineering this chip

[joeventura]

hahaha well your idea of fun and mine......

[candle]

not that funny...

just providing the way out

for me You may toss whole thing right into the dumpster

[joeventura]

Didn't mean any offense, just not the way I would fix it.

[candle]

understood

[sl0re]

On 7/6/2009 at 12:16 PM, joeventura said:

I will check.

 

Just to clarify the pics you are looking at are from two different BIT3 cards, one that does not have the problem and one that does.

 

I will swap the Char ROM chips first and see if that helps.

 

The data being input is on the same atari 800 from BASIC cart so its not what is being sent to the card or the computer as they are consistent unless you are implying that the two cards interact with the same Atari 800 differently?

Thanks for posting your troubleshooting. I have one with the same symptom. Now I have something to try.