Interface several 4021s and 4094s with PIC (say 16F84)

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Hi,

For a project of mine, I have to connect several 4021s (3 or more) for handling inputs and several 4094s (3 or more) for handling outputs. Since we all know that there are limitations in source and sink currents (so far I can remember, it is about 20mA).

My question is how many 4021s and 4094s can be directly connected to a single PIC (like 16F84/628). If I want to connect them, do I have to use buffers in between?

Please give me some idea on this; a sample schematic (if possible) will be helpful.

Thanks.
 

Hi,
Could you tell me what is 4021s and 4094s ?
I wanna be sure that Latches can be used in your case or not.
 

yes , you can !

and make all data related lines common , and seperate the clock lines , in this setup clock lines act as selection lines .
 

Hello,

Thanks for your quick response.

Sorry for the inconvenience. The chips descriptions are:

4021 = 8 stage shift register (parallel to serial) (to shift in the inputs
4094 = 8 stage shift register (serial to parallel) (to shift out the outputs serially)

The main feature these chips are, they can be cascaded one with another to form higher numbers of inputs/outputs.

Please let me know if you need further details. I found several examples using these chips with AT89S52, but could not found one with PIC. That's why I am asking.
 

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