For more info on using a PIC in place of a '922 or '923 see http://www.emags.com/epr/electron/issue1/feat0302.htm, where a sample circuit using a 16C55 is presented, which is even cheaper than the 16x84 you suggested. CIAO - Martin. On Thu, 29 Jan 1998 05:42:51 -0800, Tom Handley wrote: >At 03:10 PM 1/28/98 GMT, Martin wrote: >>First, the original question simulating key presses on an existing >>keyboard (on a VCR), and whether to use opto's or CMOS analog >>switches. A keyboard encoder chip would not solve the original >>problem. > > Martin (and Morgan), sorry about that. I missed the original thread. >I've noticed several good solutions to the original problem. > >>Also, on the topic of the 74C922, this chip has always had limited >>availability in a lot of local markets, and as you note, it is a bit >>expensive. Since a small PIC device can duplicate the functionality >>of a '922, at a lower cost, if you want to use a separate keyboard >>encoder with a PIC, it makes more sense these days to use another PIC. > > Good point about using a PIC as a dedicated controller. I have'nt >looked into this for a couple of years and I still have some 922's in >stock. I did'nt have a problem with availability but I checked Digi-Key >and noticed that they have gone up in price... You could use a 16x84 >and an R/C oscillator to do the same at about half the price... > > - Tom Martin R. Green elimar@NOSPAMbigfoot.com To reply, remove the NOSPAM from the return address. Stamp out SPAM everywhere!!!