I am hobbyist and am looking to reduce signal frequency using D type flip flops. I have a circuit diagram for a 4013 IC but I would like to use a 74HC74 instead and I do not understand if it is possible.
From wikipedia:
- 7474 are dual D positive edge triggered flip-flop, asynchronous preset and clear.
- 7479 is a dual D flip-flop
Likewise the 4000 series:
- 4013 is a Dual D Type Flip Flop
I wasn't able to find a 74HC79 components however I was able to find 74HC74 and a 4013 IC.
From looking at the functional diagram in the specifications, they are essentially the same other then that one has CD [asynchronous clear-direct input (active HIGH)] and the other has RD [asynchronous reset-direct input (active LOW)] on the diagram.
I want to construct the following diagram using 74HC74 instead of 4013:
Could this be done using 74HC74? How would such a circuit be different? or can RD be connected to the negative wire just like CD?
Best Answer
Yes, you can use a 7474 to divide by two.
BUT the set and reset inputs are active low in the 7474, whereas they are active high in the 4013.
This means that to divide by 2, the set and clear must be pulled up or connected to the rail, not to ground.
One further point, with CMOS, inputs should not be left floating, BAD things can happen. Take all inputs on unused sections of the device to rail or ground, it doesn't matter which, obviously take all used inputs to the correct logic level. Outputs should be left unconnected if not used.
Download a data sheet for both parts and study them carefully for pinout and pin function, IIRC the packages are not pin-compatible, so you will have to change the pin numbers as well.