digital logic gate (behavior in spice)

[Munyua44]

I came across the A input and the B input for the XOR gate in it spice. The output displays 1V and 0V regardless of the voltage that is applied on the input. There are many other terminals in the gate that the itspice does not explain what they are or even explain their purpose. Can anyone of you help me to understand what this other terminals are?

 

[KlausST]

Hi,

Output voltage levels of real logic circuits depend on supply voltage, but not on the signal level of logic inputs.
The output is either HIGH or LOW depending on logic input states (HIGH/LOW).

There are many different logic families.
They differ on
* supply voltage range
* supply current
* input level thresholds
* input voltage range
* output levels (vs current)
* output current capability
* ...

Klaus

 

[FvM]

You want to read the description of digital gates in LTspice help, everything explained, although not very detailed.

The output displays 1V and 0V regardless of the voltage that is applied on the input.

The expected behaviour of digital gates. Logic voltage can be configured in gate parameters.

The gate symbol is universal and has optional inputs, all with same function. Unconnected inputs are ignored.

 

[stenzer]

Hi,

have a look here http://ltwiki.org/LTspiceHelp/LTspiceHelp/A_Special_functions_.htm

BR

--- Updated Jan 29, 2022 ---

... this may help to identify the numbers of the mentioned terminals.

 

[Munyua44]

Hi,

have a look here http://ltwiki.org/LTspiceHelp/LTspiceHelp/A_Special_functions_.htm

BR

--- Updated Jan 29, 2022 ---

... this may help to identify the numbers of the mentioned terminals.

View attachment 174167

thanks so much. Number 6 and 8 are the terminals that had not been named and I can now relate.

 

[stenzer]

Hi,

in general, in LTSpice you can right click on the symbol. A pop-up apperas, in the upper left side you are able to open the symbol. In the symbol viewer you are able to determine the pin numbers (netlist order) by making a RMB click on the pin of interest.

BR