The processor polls U2 to get the current configuration of the switches. Pin 1 of U2 is pulled low which then loads the state of D0 thru D7 (/BANK1 and /BANK2 select which switches to read), The serial data is then read from U2 via pin 9 by the control board MCU, U6.
On Sat, 20 Aug 2005 12:47:14 -0700 (PDT), [EMAIL PROTECTED] wrote: >Good day all! > I was trying to understand how the keyboard signaled the controller >processor that a new key was punched but to no avail. Also, the shift >reg. (U2) notes which keys are pushed but I can't see how this works. The >inputs of U2 are pulled up with external 100k r's but the input of U2 >being a 'hc device loads the input circuitry very very little and so the >input would never go to a low logic level. > I take it that until the processor is some how notified that a key is >pushed, it remains in sleep mode. Hard for me to understand without some >help but I'm sure, you guys have the answers. > Thanks for any encouragement, Bob K7HBG > > > >_______________________________________________ >Elecraft mailing list >Post to: Elecraft@mailman.qth.net >You must be a subscriber to post to the list. >Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > >Help: http://mailman.qth.net/subscribers.htm >Elecraft web page: http://www.elecraft.com _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
