8/14/02 9:18:44 AM, Tony Pan <weidong.pan@VERIZON.NET> wrote:

>According to UL1998 an unique identifier that is computed as a function of
>the code must be stored in non-volatile memory.
>
>Does anyone have idea how this is done?
>
>(I cannot calculate the CRC or checksum because of the chip that I use.)

Would the following be permissible according to your reading of the standard?

1) Program all but one location in the chip.

2) Read the code back out after programming.

3) Calculate (on a development tool) the CRC or checksum of the read-back code.

4) Program the vacant location with that CRC or checksum.

Then it would be possible to use external equipment (an ICSP programmer or a plain programmer if the
chip is socketed) at any time to determine whether or not the code was corrupted.  This would *not*
require access to a known-good hex image of the code.

This all depends on whether or not the product has to be able to detect code corruption by means of
*self* testing (in which case it won't work).

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