We have recently had a couple of devices (16F628) with faulty RAM addresses.
Fortunately they were caught during quality control, but I'm a bit concerned
that it could have a more subtle effect, if the fault had occurred in a
different byte.

Two bytes (0x74 and 0x78) had a 'sticky' 1 in bit 6.  If I write 0xFF, I
read 0xFF, if I write 0x00, I read 0x40.

Has anyone come across this before?  It happens constantly on 1 device, and
happened intermittently on 3 others.  I've tested over 20 from the same
batch which have shown no faults.

I could add RAM checking code to the device, but code space is short, as
usual, and there would still be faults which are not detected.

Nigel



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