74ls96 function error in proteus

Thread Starter

cl4y

Joined Mar 17, 2016
23
Hi, I'm having a problem about 74ls96 5-bit shift registers, the functions seems wrong.
When I try to make the clear/preset to 00 and 10 work fines
but when clear/preset is 01 the function should allow the q point to follow their respective inputs to a 1 or 0 and it's not happening also when the clear/preset is 11 it allows the q point to follow their respective inputs from a 0 to a 1 but not from a 1 to 0,
please help thanks.
sorry for the grammar.
 

dl324

Joined Mar 30, 2015
9,326
Welcome to AAC!
when clear/preset is 01 the function should allow the q point to follow their respective inputs to a 1 or 0 and it's not happening
Clear is LOW active and must be HIGH before preset is enabled.
when the clear/preset is 11 it allows the q point to follow their respective inputs from a 0 to a 1 but not from a 1 to 0
Preset will only set a bit to 1. The expected use is to clear the registers before using preset.
 
Last edited:

Thread Starter

cl4y

Joined Mar 17, 2016
23
It can only shift right.
Sir, how can i prove to my professor that it can't shift to the left ? Cause he asked my classmates that if he can make it shift to the left he'll give them a failing grade. It is possible to make it shift left by adding some gates, and still I can insert 1 or 0 when shifting ? Thank you.
 

Thread Starter

cl4y

Joined Mar 17, 2016
23
Since this is homework, we don't do the work for you. Look at the datasheet for 74LS95 for some clues.
Sir, the 74LS96 will only shift if the Clear is 1 and Preset is 0, am I right? Can I have a last clue sir ? I don't know what to do about the clear and preset. When Clear is 1 and Preset is 0 it disable the changes from the Q points. How can I make it shift to the left, if I can't make changes in the inputs like the 74ls95, please help, this would be the last I'll ask about this. Thank you in advance..
 

dl324

Joined Mar 30, 2015
9,326
Sir, the 74LS96 will only shift if the Clear is 1 and Preset is 0, am I right? Can I have a last clue sir ? I don't know what to do about the clear and preset. When Clear is 1 and Preset is 0 it disable the changes from the Q points.
Below is the function table for the shift register. I've circled the conditions required to shift (right).
upload_2016-3-20_7-29-52.png
How can I make it shift to the left, if I can't make changes in the inputs like the 74ls95, please help, this would be the last I'll ask about this.
What year are you in your studies? Does the LS96 allow you to "preset" a 0?
 

dl324

Joined Mar 30, 2015
9,326
I'm a 3rd year student sir.
If the LS96 was capable of left shifting, how would you implement it? More specifically, how could you parallel load a zero?

If your "yes" was to my query regarding being able to "preset" a zero, read the datasheet; looking closely at the logic diagram.

Did your professor bound the amount of logic you could or should use to implement left shift?
 

Thread Starter

cl4y

Joined Mar 17, 2016
23
If the LS96 was capable of left shifting, how would you implement it? More specifically, how could you parallel load a zero?

I would implement it by connecting the outputs, to the load input, but one place out,
so QD to input C, like the 74ls95 sir. By having a Low on "preset" ?
If your "yes" was to my query regarding being able to "preset" a zero, read the datasheet; looking closely at the logic diagram.

Ah, i can't because in that case the "preset" is don't care
Did your professor bound the amount of logic you could or should use to implement left shift?
No sir, he just want me to make it shift to the left.


at the count of 7 he just wants the bit shifting to the left.
 
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dl324

Joined Mar 30, 2015
9,326
Will depend on the preset? If the preset is 0 the 1's will turn to 0, and if the preset is 1 the 1's will stay 1?
If you have a combination of 1's and 0's that you want to parallel load, how can you do it with the LS96 functionality? You can clear all bits to 0 or you can set all bits to 1; how can you handle a combination of 1's and 0's?
 

Thread Starter

cl4y

Joined Mar 17, 2016
23
If you have a combination of 1's and 0's that you want to parallel load, how can you do it with the LS96 functionality? You can clear all bits to 0 or you can set all bits to 1; how can you handle a combination of 1's and 0's?
By Having the Clear set to L and the Preset Enable to H sir, I can have the Q points to have a combination of 1's and 0's
 

dl324

Joined Mar 30, 2015
9,326
By Having the Clear set to L and the Preset Enable to H sir, I can have the Q points to have a combination of 1's and 0's
If you had 00101 in the shift register, how would you wire it to shift left? If you clear the shift register so you can "load" 0's, you lose the 1's.

Since this is an academic problem contrived by a professor divorced from reality, it can probably be done. In the real world, you would just select a more appropriate device.

BTW, I can't read part numbers from either of the schematics you posted. From what I could read, you don't have the parallel inputs of the shift register connected. To get this seven you mentioned, are you shifting serially?

Could you use the upload option on the form instead of posting on some hosting site? It serves up "advertisements" that are not Wife-friendly.
 

Thread Starter

cl4y

Joined Mar 17, 2016
23
If you had 00101 in the shift register, how would you wire it to shift left? If you clear the shift register so you can "load" 0's, you lose the 1's.

If Qa=0, Qb=0, Qc=1,Qd=0 and Qe=1, I will connect Qe to the input of Qd, output of Qd to input of Qc and so on, and Serial in to input of Qe. I will change the control lines to Clear=L and Preset Enable=H

Since this is an academic problem contrived by a professor divorced from reality, it can probably be done. In the real world, you would just select a more appropriate device.

BTW, I can't read part numbers from either of the schematics you posted. From what I could read, you don't have the parallel inputs of the shift register connected. To get this seven you mentioned, are you shifting serially?

I removed it sir, cause I was trying to connect Qe to input of Qd and so on. We're doing the Parallel In Serial Out sir. The seven sir is for the count of the 7 segment display.


Could you use the upload option on the form instead of posting on some hosting site? It serves up "advertisements" that are not Wife-friendly.

Sorry for that sir.
 

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