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AR# 3653

CPLD: XC9500: Device fails to erase when used in an embedded or ATE environment


General Description:

XC9500 devices fail to ERASE when the SVF/XSVF files are used in

an embedded system or in an ATE environment.


The erase time required by all XC9500 devices is 1.3 seconds. This time can be extended in the presence of any or all the

following situations:

(a) low or noisy SYSTEM Vcc - typically a Vcc at or above 5V is required. The Vcc connections must have adequate

decoupling at each device.

(b) Excessive SYSTEM ground noise - a solid ground signal is required to ensure effective operation of the internal charge


(c) Inaccurate implementation of the wait time procedure - ideally the wait time should be implemented independent of TCK.

Preferably it should be implemented as a wait time dependent on an internal independent clock for best accuracy.

JTAGProgrammer can sometimes compensate for these situations because in its interactions with the system it can determine

that the devices need longer to erase and adjust the value as appropriate.

SVF files, since they are statically generated, do not have that luxury of being able to interact with the system and modify

their behavior as appropriate.

Note: Bumping up the ERASE times to 3 seconds should be enough.

AR# 3653
Date Created 08/21/2007
Last Updated 05/07/2014
Status Archive
Type General Article