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Topic: DM74LS47N 7seg Decoder wiring (Read 931 times) previous topic - next topic

fubbi


Hello

Does someone know how to wire up a DM74LS47N? (http://www.alldatasheet.com/datasheet-pdf/pdf/51079/FAIRCHILD/DM74LS47N.html)
The outputs for the segments are obvious but I do not understand the inputs.

I need to hook up 4 of them.

Thank you!

Fubbi

Grumpy_Mike

#1
Nov 22, 2011, 10:50 am Last Edit: Nov 22, 2011, 10:52 am by Grumpy_Mike Reason: 1
The four inputs A0 to A3 define the number you will display.
~LT is the lamp test and should be wired high for normal operation.
The ripple blanking input depends on how you intend to wire them up. Are you going to multiplex the display or are the displays going to be on all the time?
But basically it allows leading zero suppression in multi digit displays, if that is what you want.

fubbi

How can I chain 4 of them? or do i need all those outputs for each chip?

thanks

fubbi

Grumpy_Mike

If the displays are going to be on all the time then yes you need separate outputs for the A0 to A3 inputs. Best done with two shift registers.
If you are going to multiplex them then you only need have one set of outputs for the A0 to A3 inputs as well as switching the anodes. In fact you only need one 74LS47.

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