I want to do a down counter using 74ls193 .i want to start from 159 to 0 .my problem is that, i cannot make the second 7segment count from 9 to 0 because it always load 5.

Um... this is more of a computer hardware and software board, but your question seems to be very much on the electronics side of things. You might have more success solving your question on an electronics forum :)

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