View Full Version : OT: Info on a GI 8521 IC?

04-27-2009, 12:09 AM
On the keyboard on my cnc lathe the encoder chip is a General Instruments GI8521CCA. 40Pin DIP Package. Handles scanning the keyboard.

Anyone have any info on it. Dont know where else to ask.

04-27-2009, 12:48 AM
The 8521 is the same as the 6526 CIA (Complex Interface Adapter). I probably have a data sheet and the spare part as well. Do you need one?

Here is the datasheet.


04-27-2009, 01:06 AM
Thanks Evan. I kinda figured you would know!

Dont think I need one. Hoping I can reuse the keyboard somehow on the Hercus lathe. Looks like with that data sheet I can trace out the data lines on the board and maybe use some sort of microcontroller to talk to the PC. Or do you know of an IC that would talk to the PC via USB or the PS2 connection?

04-27-2009, 04:09 AM
These guys have some pretty interesting USB I/O boards. A little more expensive than building your own from a chip but it takes all the uncertainty out of the job.


BTW, I have ordered from them twice with no issues.

Note: the 6526 is not a keyboard controller. It's a parallel I/O chip with some system clock run timers and convenient interrupt generation and overflow handling. To actually use it to scan a keyboard matrix requires that you implement the scanning routines. The chip has two 8 bit I/O registers so can directly cover a 64 key matrix and with some fiddling that can be doubled by using the serial i/o pin, if I recall correctly.