I was looking at the STK500 schematic and wondered how the different IC's are multiplexed?
I saw that all the similar function pins from the different sockets (e.g.port A,B,C,D pins) are bussed together and labeled as PAT[7..0] etc.
Here is a stupid question: If there are more than 8 pins of say port A multiplexed, why is it labeled as PAT[7..0]? Is it just the standard 8 bit bus notation?
Also I saw on sheet 7 that say, the port A pins are separated and connected to J702,J706,etc. Are these switches? Then they are connected to J700 on both sides. Why is that?
I would greatly appreciate it if any of you has seen a detailed circuit explanation of the STK500 schematic. I did search on the forum and found Colin O'Flynn's notes on repairing an STK500 but it does not go into details of this multiplexing of different AVR's.
Thanks for your patience.