[Yocto-bsp] error for an bitbake command

[prasad yerramsetti]

Hi,
when i try to build or download the source code from openembedded for
picochip i am getting the following below error for any bitbake commad.

ERROR: Please set the 'PERSISTENT_DIR' or 'CACHE' variable.

can you tell where might be the problem.
even i searched for this error,but i could n't find exact solution.
if anybody tell,this is greate help for me.

Thanks
prasad
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