Need A Digtal Expert!

i have designed this counter to count like ( 4, 2, 5, 0, 3 ) and repeat .

i followed the excitation table of T flipflop but.!


it doing partially wrong (0, 6, 1, 2, 5 ) and repeat

i don't know what's wrong , please check the schemtic and tell me where is the wrong part.

Let me accept that I am no expert and what we have learnt, we forgot over a period.
But, I feel that, the switch used to input data needs to be modified, as the present arrangement does creates noisy spikes due to contact bounce. Generally they use a two NAND gate configuration with proper pull ups and with a change over switch..

Secondly, perhaps the input pins of unused gates of 7404 can be connected to ground or battery. This would help reducing floating gates creating unwanted noise. It has been followed in the case of 74LS73.

Also, each old TTL IC needs a 0.1uF ceramic disc supply bypass capacitor.
I hope the supply is regulated at 5.0V.

Also the S and R of the 7476 are active low so they should connected high and not float.

Yet another mod. the display driver outputs shall, better have limiting resistors, even if the segment outputs have current limiting feature.

haven't goon through it, but you have 5 states listed. this would seem to leave invalid states possible. the intended cycle is the path listed, but do any of the invalid states connect to itself, or a path that returns to itself (eg, a second possible cycle).

basically, you might have 2 or more possible solutions to your circuit, based on the initial condition, which might be random, or favor some unknown but consistant value.

it works but just when i reveresed the input to the seven segment driver 74ls47

watzmann said:

it works but just when i reveresed the input to the seven segment driver 74ls47

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After interchanging A & C inputs to the 74247, is it consistent in giving result?