S100 address buss troubleshooting

Richard A. Cini rcini at optonline.net
Sat Jun 4 17:26:34 CDT 2005


	After verifying the power supply, I'm now starting to play with the
system. I put in the CPU board (TDL Z80) and three 16k memory boards.
Reading and writing data to memory seems to work, but frequently I'll get
the A13 and A7 LEDs stuck ON. If I toggle RESET, the LEDs clear but on my
first EXAMINE, A13 and A7 go on.

	Things I have not done yet:
	* loaded any programs or tried to verify memory fully
	* cleaned any board contacts

	If I pull one of the memory boards, the A7 problem goes away but A13
stays on all the time, leading me to believe that that issue is either on
the CPU card or the front panel card.

	How does one troubleshoot a stuck-bit problem in these systems? I do
have a 12-bit logic analyzer on a laptop (uses the parallel port) but I
haven't pulled that out yet.



Rich Cini
Collector of classic computers
Build Master for the Altair32 Emulation Project
Web site: http://highgate.comm.sfu.ca/~rcini/classiccmp/

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