74161 vs 74161N
My understanding is that the N does denote anything about the logic or timing in any way - but is a packaging marking
"The N suffix on the part number is a vendor-specific code indicating PDIP packaging....PDIP =Plastic DIP (PDIP) packages" whcih means the housing is made of plastic instead of other material (such as cheramics)
DIP package = an electronic component package with a rectangular housing and two parallel rows of electrical connecting pins
I tried the Proteus 8 Demo SW. The demo does not allow you to save files unfortunately. I tried a 74161 version which was marked as for "simulation". I was not able to find a way of looking insde their model construct.
I read the datasheet (http://www.ti.com/lit/ds/symlink/sn74161.pdf ; page 2) more carefully and now it is clear to me that ENT should be fed forward to enable ripple carry output that can be used for succescive cascading; wheras ENP is just an enabler.
I also had a friend (with deep IC design skills) look at the logic diagram on page 4 and he concluded that it appears that ENT and ENP logic has been swapped in the multisim model (or simply their labels have been swapped)
Thanks for your feedback!
First some feedback from my side:
- I was also aware of that note in the wiki, but I was thinking more in the sense of which vendor "provided the model".
If one vendor of the PDIP version provided an incorrect model, then the source could be even deeper.
That left aside, this issue still should be reported to R&D (and will be)
For a solution to the problems:
At my side changing the model at one line did the trick.
In attachment there is a capture of the model line I changed (swapped ENT and ENP).
Please make a back-up before updating all components of this type.
- Can you verify that this produces the behavior you expect?
- Or is there still something wrong?
I want to make sure that we come to the correct/expected behavior of the model, before requesting the change towards R&D.
My trial period expired yesterday so I cannot test your proposed solution (although I believe it makes sense) - Unfortunately I spent most time trying to understand the 74161 issue before being able to actually try out your product
Would there be a way to extend the trial period?
One way I think you could kind of extend is is to try to download a different version of Multisim (Educational).
Alternatively you could also try to use it on another pc.
It's three years later, and the newly-downloaded model for the 74161 is still incorrrect: the behavior of ENP and ENT are swapped. This caused me to waste a day trying to understand what I was doing wrong, but it wasn't me.