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AR# 21760

Spartan-3 DCM - What is the purpose of the CLKIN_PERIOD attribute?

Description

Is it absolutely critical that I specify the DCM input clock period via the CLKIN_PERIOD attribute?

Solution

Unlike other architectures, it is not critical that you set the CLKIN_PERIOD attribute when targeting a Spartan-3 because this attribute is not used when configuring the DCM. However, setting this attribute is not harmful because it will help the implementation tool perform more accurate DRC checks on the DCM. For example, the CLKIN_PERIOD setting is cross-referenced against the FREQUENCY_MODE setting to ensure that the correct frequency mode is set.

AR# 21760
Date Created 09/04/2007
Last Updated 12/15/2012
Status Active
Type General Article