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AR# 5346

Exemplar: How to infer STARTUP, using the infer_gsr command.


General Description:

Using Exemplar Leonardo how can I get the STARTUP block into my design

to utilize the dedicated resources on the Xilinx chips?


1) One way is to instantiate the STARTUP block the bring the signal going to

the GSR pin on the STARTUP out to a port. Then in the HDL code describe

an asynchronous set/reset signal with the same name as the STARTUP's

GSR port name.

2) The Exemplar tools can also infer the STARTUP component by using the

infer_gsr command. Every flip-flop in the design must have a common

asynchronous set/reset signal in order for STARTUP to be inferred. This

coding technique will also allow more accruate RTL simulation by

matching up with expected results. You can still have an additional

asynchronous reset, such as to set/reset one flip-flop, while still

having synthesis infer the STARTUP by following the above coding style.

This will result in the GSR from the dedicated resources being OR'd

with the additional reset using a dedicated OR, (NOT an additional LUT).

To utilize inferring of STARTUP do the following:

a) If you are using the GUI make sure the "Assign GSR" box is set to

in the auto in the Technology tab. You can also use the "Manual"

check box and name the signal which you desire to be active high

set or reset.

b) If you are using a Tcl script use the infer_gsr command or use the

global_sr command to assign an active high signal name as global set or

AR# 5346
Date Created 08/31/2007
Last Updated 07/27/2011
Status Archive
Type General Article