Re: TECH: Couple more TEMPEST questions

On Sat, 08 May 2004 20:31:36 -0500, you wrote:

>Are the IC pins labeled as not "G" on the Tempest schems not "ground?" If
>so, they should be at a steady high logic level, right? On my boardset, some
>are low and some are pulsing. Specifically, A/B1 and B/C1, pins 1 and 19 on
>the main board are low. F2(8304B) pin 9 and H2(new LS245) pin 19, both on
>the main board, are pulsing. H3 pins 1 and 19 on the aux. board are low.

        Actually, no. On the 74LS245, G* is a controls the tri-stating of the
bus. When G* is high, the A and B inputs go into their high-Z
(high-impedance) state; when G* is low, then data flows from A to B or from
B to A depending on the state of the DIR input.
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solarfox@DON'TMESSWITHtexas.net (Gary Akins jr.)
http://lonestar.texas.net/~solarfox
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Received on Sat May 8 22:38:39 2004