TI 99 32k RAM card errors

[eccofonic]

I finally got around to further testiing the 32k RAM card that I mentioned at the end of this thread:

 

http://atariage.com/forums/topic/227990-ti-99-disk-controller-question/

 

I've also since found another card that's working properly.

 

I tested the bad card with the TI 99 Diagnostic disk (P/CARDS program)....

 

... which halts immediately with an error when testing area "2000".

 

I also tested it with basic program using mini-memory.

 

I think I found that program on here, but I rewrote it to let me input one address at a time and test all bits individually.

 

Consider the bits being 1 thru 8 or rather... 1,2,4,8,16,32,64,128

 

Anyway, here's the results:

 

from 8192 to 16383: in every location tried, bit 2 is stuck on. So a CALL LOAD (10124,0) would result in 2 when PEEK'd.

 

from -8192 to -1 no errors

 

from -16384 to -8193 no errors

 

from -24576 to -16385 in every location tried, bit 2 is stuck off. So a CALL LOAD (-20124,2) would result in 0 when PEEK'd.

 

Any guru out there know which chip this is? I haven't found any schematics out there yet.

Edited October 9, 2014 by eccofonic

[+Ksarul]

You might want to look on Mainbyte's pages, specifically here:

 

http://mainbyte.com/ti99/schematic/schematics.html

 

He has schematics for most of the regular TI cards, including the 32K card. . .