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AR# 11741

4.2i Foundation Aldec - How do I put the information from an output back on a input of the device without changing the netlist?

Description

Keywords: Foundation, Aldec, Simulator, input, output, transfer

Urgency: Standard

General Description:
I would like to feed the output of a device back into it via a separate input. In a VHDL testbench, I would just assign a signal between these two pins. Can I do the same in the Aldec simulator?

Solution

There is no direct way to do this in the Foundation Logic simulator. However, this functionality can be achieved by writing the output to a file, then reading it back in to the input.

On each change of the output signal its value is written to a file. On the same change this value is read back from the file and assigned to the input pin.

The following is a sample command file:

|-------------------------------------------------
restart
delete_signals
watch a b output endout input
| a and b are the inputs for the first function (e.g. an and-gate)
| output is the output of the first function
| input is the input of the second function
| endout the output of the second function

wfm a 0=0 (10ns=1 10ns=0)*10
wfm b 0=0 (20ns=1 20ns=0)*5

break output ? do (check output > mytest.dat;assign input < mytest.dat )
| on each change of the signal output its value is written into 'mytest.dat'
| and read back and assigned to 'input'
sim 200ns
|------------------------------------------

The drawback to this method is that the simulation will be slowed due to the file access operations; however, it is useful because the simulation can be completed without user intervention.
AR# 11741
Date Created 06/07/2001
Last Updated 08/11/2003
Status Archive
Type General Article