All About Circuits Forum Designing a 16-4 priority encoder from 2 74148 8-to-3 line priority encoder device
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#1
03-17-2009, 01:55 AM
 hitmen Senior Member Join Date: Sep 2008 Posts: 156
Designing a 16-4 priority encoder from 2 74148 8-to-3 line priority encoder device

Hi all,

My tutor gave me an answer I did not understand.
I searched the datasheet of 74148 but it did not specify what is GS, E0 and E1.

I also do not understand why the E1 of one 74148 is connected to the E0 of another.

Can anyone help?
#2
03-17-2009, 02:04 AM
 beenthere Senior Member Join Date: Apr 2004 Location: Missouri, USA (GMT -6) Posts: 15,815 Blog Entries: 10

All you have to do is look at the truth table to see what conditions set GS low and EO low. You can also see the effect of the EI^ input (hint - when it is high, what happens to the outputs, including GS^ and EO^?).
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First comes the hardware, then the software.
#3
03-24-2009, 10:25 AM
 hitmen Senior Member Join Date: Sep 2008 Posts: 156

Well, I got the answer from my tutor but there is one thing I dont understand. What does GS stands for?

I learnt from my tutor that:

1) The IC that displays the MSB have to be disabled if it is below a certain level.

2) The outputs from each gate have to be AND together to produce the desired output.

I know that E is enable while I0 to I7 are the inputs while thost starting with A are the outputs.
And I still dunno what GS stands for?
#4
03-24-2009, 11:22 AM
 thatoneguy Senior Member Join Date: Feb 2009 Location: Midwest USA Posts: 6,356 Blog Entries: 4

GS is "Group Output" - goes low on priority detect, with priority address in A0-3, also active low, combined with GS to flag which IC when cascading two.
#5
03-24-2009, 12:05 PM
 beenthere Senior Member Join Date: Apr 2004 Location: Missouri, USA (GMT -6) Posts: 15,815 Blog Entries: 10

Googling "74148" will let you find a data sheet for the device.
__________________
First comes the hardware, then the software.

 Tags 164, 8to3, designing, device, encoder, line, priority

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