Sony Checksum protocol

dormie1360
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Sony Checksum protocol

Postby dormie1360 » Sun Nov 30, 2008 3:08 pm

Could someone explain to me in simple terms how Sony figures the checksum for their devices. I have their protocol docs, but I don't understand when they talk about "low rank" and "set to 0".

I have some strings that work, but I still can't "reverse engineer' the CS to see how it was derived.

Thanks,
John

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Postby davew01 » Sun Nov 30, 2008 3:21 pm

I would apply the "lowest 10 scores" method
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CinemarDave
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Postby CinemarDave » Sun Nov 30, 2008 4:27 pm

You need to do byte level additions. If you add two bytes and the total is more than 255 you ignore the overflow. Your result will always be a value between 0 and 255.

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Sony Checksums

Postby davew01 » Mon Dec 22, 2008 10:29 am

Hi Dormie1360 -

Looks like you did not get much help regarding your post from the Sony experts out there. Let's see if the attached information clarifies the outstanding question. The first document "Hand Calculate Sony Checksums.pdf" is a quick explanation I put together of how to use the calculator in MS XP to calculate checksums in a serial transmission between a Sony changer and a serial master device.

The second document is an Excel spreadsheet method to calculate the checksums. It uses built-in Excel functions to perform the calculations. The spreadsheet also includes a partial list of changer checksums.

Hopefully this information will help.

I could build the calculator into an iPhone application if you like.

Davew01
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Dave W.

dormie1360
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Postby dormie1360 » Thu Dec 25, 2008 2:17 pm

Thanks to everyone, all is well.

John


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