On Thu, 14 Oct 2004, Denny Esterline wrote:

> I had forgotten that trick. Would work fine, but James pointed me to a way
> to get there with four NAND gates, which will work out for me.

Just in case you're building a counter using a pic, my favorite 
multiplexer is a resistor:


                            +----prescaler clk out (RA3)
                            |
in (low z) --R1(330Ohms)---*----counter input (RTCC for 16C54 ;-)

In my pic based counter (long time ago), I used a single section of 74HC00 
wired as inverter, as buffer to drive the low z point. The counter was 
tested to beyond 28MHz and would probably work to 50MHz. When RA3 is high 
Z input pulses reach RTCC via R1. When RA3 is output it both forces the 
RTCC input to the desired level (H or L) and can be used to clock out the 
prescaler.

Peter
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