8T97 == 74367 ?? (IMSAI front panel)

From: Dwight Elvey <elvey_at_hal.com>
Date: Wed Jun 30 16:55:11 1999

"Bill Sudbrink" <bill_at_chipware.com> wrote:
> > I could figure out what was the source of the troubles.
> > Dwight
>
> Pin 1 - 8080 D0 (pin 10)
> Pin 2 - 8080 D1 (pin 9)
> Pin 3 - 8080 D2 (pin 8)
> Pin 4 - 8080 D3 (pin 7)
> Pin 5 - 8080 D4 (pin 3)
> Pin 6 - 8080 D5 (pin 4)
> Pin 7 - 8080 D6 (pin 5)
> Pin 8 - 8080 D7 (pin 6)
>
> Pin 9 to 16 no connection.

Great!
 This explains why inverting doesn't work. If you invert the connector,
you connect the signals to 9 thru 16. Since these are not connected,
you get strange behavior.
 My first thought is that one end of the cable was poorly crimped
and the ribbon is shifted sideways by one pin ( I've seen this happen ).
The next thought is to simply connect up pins 1 to 16, 2 to 15 ....
8 to 9. Now when you invert the connector, it will reverse the data
and you'll be back in business.
 Don't waste time on the 7405 or 8T97, they can't cause the symptoms you
describe. Remember, the first rule of trouble shooting. The
solution has to solve the symptoms. How could a logic part swap
the data lines by a failure? I've never seen it happen. It can
open the lines or short the lines or even leave out one or two.
Dwight
Received on Wed Jun 30 1999 - 16:55:11 BST