Computer Architecture

[harry2]

Hi,

 

For my architecture work I need to identify the 4-bit register with tri-state outputs 74LS173 and the 4-bit ALU 74LS181.I need to research their operation and design and simulate a test layout for each, using logic switches to input data and logic displays to show outputs, and 4-bit data items and pathways.

 

Can anyone give me some ideas on how to get started? Thanks.

Edited February 1, 2012 by h2o v2

[TonyMcC]

Hi,

 

For my architecture work I need to identify the 4-bit register with tri-state outputs 74LS173 and the 4-bit ALU 74LS181.I need to research their operation and design and simulate a test layout for each, using logic switches to input data and logic displays to show outputs, and 4-bit data items and pathways.

 

Can anyone give me some ideas on how to get started? Thanks.

 

I suppose you would have to break things down a bit. i.e. be clear in your own mind on what the various terms mean. 4 bit register: tri-state: data sheet for 74LS173: data sheet for ALU 74LS181: 4 bit data systems and pathways. If you haven't text book information then you could use google.

This would give you a firm basis for considering what you need to do to achieve your aim. You could then submit your idea(s) in the form of a diagram(s) for comment on the forum.

Edited February 1, 2012 by TonyMcC

[Xittenn]

Motorola datasheets provide a logic diagram and truth table for each of these chips. The question is asking you to make an equivalent circuit using more basic building blocks. Looking over the logic diagram and truth table should make this task rather simple.

[harry2]

Motorola datasheets provide a logic diagram and truth table for each of these chips. The question is asking you to make an equivalent circuit using more basic building blocks. Looking over the logic diagram and truth table should make this task rather simple.

 

Thanks! I had a look at the truth table and I'm a bit unsure what it all means. I'm used to seeing truth tables with just O or I - off or on. There's lots of weird symbols in there so I'm not quite sure what they mean in terms of simulating that symbol in the circuit? Do you have any ideas?

[Schrödinger's hat]

Thanks! I had a look at the truth table and I'm a bit unsure what it all means. I'm used to seeing truth tables with just O or I - off or on. There's lots of weird symbols in there so I'm not quite sure what they mean in terms of simulating that symbol in the circuit? Do you have any ideas?

 

H and L for high and low will be your off and on (I don't know if H is always on).

The funny squiggle is a rising edge. (A signal that has just turned on).

Qn seems to be some kind of variable value, I'm not 100% sure what it means in this context, but I would conjecture that it means they will retain their previous value, or will be set depending on the value of the corresponding Dn (ie. Q1 will be set to D1 on the bottom two rows).

This fits with MR resetting them to L and the fact that they will only change if the corresponding D (input) is high or low.

So Q3 would maintain the value that Q3 last had, unless MR was high (in which case it would go low) or both of the input enable values were low.

In the second case (both IE values are low) then Q3 will be set to whatever D3 is when the clock pulse goes from 0 to 1 (the chip detects a rising edge on CP).

Also, as long as the clock signal remains low, Q3 will be kept at its current value.

[harry2]

Thanks!

 

I'm trying to simulate the circuit in circuit maker, do you happen to know what the 3 "box" shaped objects in the middle of the logic diagram are called?

 

http://www.datasheetcatalog.org/datasheet/motorola/SN74LS173N.pdf

[Xittenn]

If you are referring to the four units with inputs/outputs CP, D, Q, and Q, these would be units of memory and are probably similar to a flip/flop circuit. Although less likely, if you are referring to the four triangle units with three inputs/outputs, than these are three state devices. The memory device may or may not be present in circuit maker, I wouldn't know, I have never used it. If not, than I suggest modifying a flip/flop circuit to match the logic table provided. I am no expert on the subject however.

[harry2]

If you are referring to the four units with inputs/outputs CP, D, Q, and Q, these would be units of memory and are probably similar to a flip/flop circuit. Although less likely, if you are referring to the four triangle units with three inputs/outputs, than these are three state devices. The memory device may or may not be present in circuit maker, I wouldn't know, I have never used it. If not, than I suggest modifying a flip/flop circuit to match the logic table provided. I am no expert on the subject however.

 

Thank you! Was referring to "the four units with inputs/outputs, CP, D, Q, and Q" yes. You're totally right, I just had a look around in CircuitMaker and there are some flip/flop circuits (that look similar to the diagram) - just have to find the right one now!

 

I'm a bit confused though.. do you think the task I've been given is really as simple as re-creating the circuit that is in the logic diagram?

Edited February 2, 2012 by h2o v2