hi evwi one!

we have this experiment in our eletronics lab that makes use of a 4-bit binary counter (74LS193). we have succesfully constructed the up and down counter, there are not much problems regarding the circuit counting up and will reset at decimal ten(binary 1010) meaning it starts counting from zero to nine, our problem is, :?: how can we count down from nine to zero :?: . we have tried to manipulate the circuit but instead it starts from 16 to zero then it got stuck at zero :cry: . i hope you could help :lol:

 

P0 (pin15), P1 (pin1), P2 (pin10), P3 (pin9) Are the parallel load inputs, You have to hardwire a '9' on these inputs

(P0 = 1, P1 = 0, P2 = 0, P3 = 1)
Then after the chip is powered on you should momentairily hold PL (pin 11) low. This will 'parallel load' the value to the chip.

You can then use CPD (pin 4) to count down.

The chip has a borrow output. (pin 13). If you feed this back to the PL pin, the chip should parallel load again after going below 0

 

hello exo,

we've tried hardwiring it 1001(decimal 9) and doing your suggestions, but it isnt working. :cry: maybe we should add another circuit for it.. :?:

thanks anyway.

 

In addition to putting 1001 on the data (preset) inputs, connect the borrow output (pin 13) to the load input (pin 1). This should make the count recycle back to 9 after reaching zero.

 

Hi, on the 74193 4 bit counter, pin 4 is ICD or count down and pin 5
is ICU or count up. When your counter reaches the desired level or number, your going to have to make pin 4 high and pin 5 low. This tell the circuit that you want to now count down not up,if you dont't do it this way it will not work because pin 4 and 5 are HIGH and the circuit will not understand what you want... I hope this will help you... :lol:

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Electronics Wizzard