8 bit counter using two 4 bit counters

[gut_but]

hi
pls anybody can help me in designing a 8 bit counter using 4 bit counter since i hav already designed a 4 bit counter. what is additional circuitry that is needed to cascade both counters and build a 8 bit counter.

electronic novice

 

[ljcox]

Connect the output of one to the input of the other.

Len

 

[ag]

connect the 'carry out' pin of the first to the 'clock' / 'count' pin of the next. When the first counter "overflows" ie is "1111", the carry bit will change to "1". If you don't have a carry bit use a 4 bit AND. Basic logic.

 

[ljcox]

connect the 'carry out' pin of the first to the 'clock' / 'count' pin of the next. When the first counter "overflows" ie is "1111", the carry bit will change to "1". If you don't have a carry bit use a 4 bit AND. Basic logic.

You don't need the AND gate, simply connect the Ck of the second stage to the most significant bit (usually called Q4) of the first stage.

Besides, the output of the AND gate is likely to contain "decoding spikes" that will cause the second counter to increment when you don't want it to.

Len