Why does the erase time required by the 9500 devices seem to
vary from system to system when SVF files are used?
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
(a) low or noisy SYSTEM Vcc - typically a Vcc at or above 5V is
required. The Vcc connections must have adequate decoupling at
(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
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.