AR# 4475

Description

General description:

Why does the erase time required by the 9500 devices seem to

vary from system to system when SVF files are used?

Solution

The erase time required by all XC9500 devices is 2.6 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 pumps.

(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.