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AR# 24677

GTP SmartModel - GTP txn/txp outputs always 'X' if TXPOWERDOWN#_IN is 'X' at start of simulation

Description

In (UniSim) functional simulation or (SimPrim) timing simulation, if TXPOWERDOWN#_IN is 'X', this causes GTP outputs TXN/TXP to always be 'X'. If TXPOWERDOWN#_IN never goes to 'X', I do not see the problem.

Solution

If TXPOWERDOWN#_IN is tied low and not used by user logic, there is not a problem.

If TXPOWERDOWN#_IN is controlled in the FPGA logic:

- For functional simulation, this can be avoided by never allowing TXPOWERDOWN#_IN to be 'X'. If this cannot be easily avoided, the simulation will also recover if TXPOWERDOWN#_IN is toggled to '1' and then a '0'.

- For timing simulation, routing delays cause it to be unavoidable for TXPOWERDOWN#_IN to not be 'X' for a very short time at the start of simulation. The simulation will recover if TXPOWERDOWN#_IN is toggled to '1' and then a '0'.

AR# 24677
Date Created 09/04/2007
Last Updated 12/15/2012
Status Active
Type General Article