ammrk@swpyr2.sbc.com (Mike R. Kraml) (04/30/91)
I am having a strange problem with the Parallel port CIA register. Bottom line, when I try to read or write to Port B of the CIA used for the parallel port, the machine resets. I wrote a simple C program that sets the DDR, no problem, then it trys to read or write to the parallel port, problem, the system does a reset, no Guru, just reset. I discovered the problem when I tried to print, the system reset. When I would remove the printer cable, the system would wait, give a printer problem requester, and just sit there. When I re-attached the printer (making it online also), the system would try to write to the port and boom, reset. I have replaced both 8520s (twice, I have several spares (all good)), the Gary has been replaced, the Agnus, the Paula, the 68000, the Denise, the 74ls32 (u37), the 74ls38 (u36), all DRAM, the 1.2 ROM, basically everything except the latches and buffers on the data bus, and the 74ls157 multiplexer to the joystick ports. Not a whole lot left. Oh, the reason all this has been replaced is that the motherboard had 12V feed to the 5V line, and took most everything out. A short blast, non the less, a deadly one. Anyway, all other functions are fine. I have tested all other I/O on the motherboard, and everything else works fine, including the other 8520. Man, I am stuck. I can only guess that its somewhere in the addressing of the CIA's registers, or the CIA is putting garbage on the data bus at the wrong time, but why? I have replaced everything in its path. Oh ya, when I did the CIA test (R/W), I Disabled() multitasking, tried to shut most everything else down, and the same thing happens: when ever I access that register for read or write, the system resets. HELP!!! Also, the Fat Agnus socket has also been replaced (that socket is nasty), anyway, I traced all lines to and from the socket to make sure there were no breaks, also checked for neighboring shorts, all seems fine. Any Ideas anyone? Thanks in advance, Mike... -- ============================================================================= Mike Kraml - Manager-Separations Mechanization - SWBT - Finance Department One Bell Center - 30-D-06 - St. Louis, Mo. 63101 PHONE: 314-235-8012 UUCP: {uunet, bellcore, texbell}...!swpyr2.sbc.com!ammrk
jap@convex.cl.msu.edu (Joe Porkka) (05/01/91)
ammrk@swpyr2.sbc.com (Mike R. Kraml) writes: > Any Ideas anyone? > Thanks in advance, Mike... Have you checked your printer cable? Try it with another computer or try another Amiga printer cable.