Author Topic: P89C668 Checksum locations  (Read 4617 times)

James McC

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P89C668 Checksum locations
« on: September 29, 2006, 05:00:50 am »
Hi Guys ,

Been using FM for a while now: loving it by the way.......here it comes BUT
when I recently started experiencing some odd code behaviour and could not understand why I took the wrong path altogether and started to retrace my code revisions to see if I could track it down :-(

After fully exhasting that (and myself) I started to cruise the forum for some help. Firstly I had been using v1.96 so I downloaded v3.31 (a good place to start you say and why did I not do that ages ago).

When programming with v3.31 and selecting 'Gen Block Checksums' I now get the warning 'Programming the checksums without allocating flash locations for them will corrupt your code' and alarm bells started going off.

The location of these checksums was causing the odd behaviour i was seeing.

Why do these checksums appear here and how can I allocate them to a different part of memory to stop this happening in the future?

Also when I view the information of the hex file the CRC differs from these checksums anyway, is this normal and if so what is the CRC for then?

Thanks in advance.
James

Andy Ayre

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Re: P89C668 Checksum locations
« Reply #1 on: September 29, 2006, 08:42:24 am »
It's not possible to change the checksum locations.
The checksums are calculated using a simple method that is quick and easy for an application to use each time it starts up. CRCs on the other hand are slower and more complex.

Please see the chapter in the manual on these Flash Magic generate checksums, what they are, how you can use them, etc.

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