Delay RAM - 14-bit Compress

Hardware questions and issues with the FV-1

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ehughes
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Joined: Thu Aug 16, 2007 4:18 pm

Delay RAM - 14-bit Compress

Post by ehughes »

I have alot of experience with high end DSPs (TI C6713 for example) but have been looking for a device such as this one for a tiny application.

I do have one question about the Delay RAM. I read in the knowledge base that the ADC is 24-bit but the Delay RAM is a 14-bit floating point format.

Now, when a code is put into delay RAM, is it quantized or compressed? If I were to put in any random code on one cycle into the delay ram and then pull it out on the next, would I get the same code?

No matter which way you cut it, a 24-bit binary number can be used to represent 2^24 entities. Fixed point, floating point, Super Monkey Bananna point, all the representations still revolve around the fact that an n bit binary number can represent 2^24 things, not matter what those things are.

I would be a little concerned if my codes were truncated. Do you use some sort of fully reversable compression?


Also, how can I get my hands on a development board and how much are they (in the US)?

Thanks,
Eli Hughes
frank
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Post by frank »

When going from fixed point to floating point there may be truncation. Basically larger values will be truncated and smaller values won't.

If this is an issue for your program and your delays aren't too long then you can increase the floating point resolution. Find the error by writing the value to RAM and reading it back, subtract it from the original value and save this difference to RAM. Then when you read back read both values back and add them together. You may still suffer some truncation but it will be just the last few LSBs.

If you need the values as the delay element in a filter then use the internal registers and not the delay RAM.
Frank Thomson
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ehughes
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Joined: Thu Aug 16, 2007 4:18 pm

Post by ehughes »

Oh Ok. Thanks for the info. I don't think this will be a problem for me but since I have access to the error term, there is a work around.


That being said, Good job on the Chip. Its a nice design for its purpose. I love the fact that the ADCs/DACs are integrated.
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