Synchronous 4-Bit Up/Down Counters preset

binarycmoscounterdigital-logicttl

I have a synchronous 4-bit up/down counter, and in the data sheet it stands that there are 4 pins where I can enter a 4 bit preset number, but it doesn't say what this number represents. I believe that it is the first number in the counting sequence (e.g. if preset is 0001, the counter will start from 0010), am I right?

Best Answer

The 74HC192/3 have asynchronous load. As soon as** you assert the /LOAD input, the outputs will change to reflect the 4-bit input you have applied to the PRESET inputs, and the outputs stay there as long as /LOAD is low regardless of clock or anything else (except RESET which overrides the /LOAD).

When you remove the /LOAD (and RESET is not active) then the counter may count up or down from the preset number, if it receives a rising clock edge on one of the clock inputs.

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** after some tens of nanoseconds with a 5V supply