What are the functional differences between the 74190, 74191, 74192 and the 74193 synchronous up/down counters

Answer 1

74190 and 74192 are decade counters (counts 0 to 9)

74191 and 74193 are binary counters (counts 0 to 15)

74190 and 74191 have a single clock, an input to select counting up or down, a count enable input, and outputs for ripple-count-out and min/max count.

74192 and 74193 have separate clocks for counting up or down, a clear input, and outputs for carry and borrow.

All 4 are asynchrounosly parallel-loadable.

Here are the datasheets:

http://focus.ti.com/lit/ds/symlink/sn74190.pdf
http://focus.ti.com/lit/ds/symlink/sn74192.pdf

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Answer 2

74191 Counter