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Visitor anirban1988
Visitor
7,688 Views
Registered: ‎08-20-2014

BRAM behaving oddly

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I have an inferred single port read-first BRAM (4096word x 1bit). I am seeing an odd behaviour that I can't pin down.

 

I have ADCs that are sending in clocked data. I then have the data stored in the BRAM and then read out. The first bit coming out is always '1' followed by the correct sequence of data bits which are shifted right by 1-bit.

 

I can always ignore the first bit and get the data, but I still need to characterize the issue, in case the behaviour changes in the future. Currently I am out of ideas as to why this could be happening.

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Visitor anirban1988
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12,861 Views
Registered: ‎08-20-2014

Re: BRAM behaving oddly

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Looks like it was some error in my control logic for the data reading process. I completely rewrote my logic generation and the problem is solved.

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Observer sunemai
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7,683 Views
Registered: ‎08-26-2014

Re: BRAM behaving oddly

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Hi,

 

Two random ideas you might consider, but none of them directly related to the BRAM itself:

 

1: Some ADCs with serial output support a self-clocked mode where a start bit is clocked out before the actual data. Maybe this is your 1-bit?

 

2: I know of at least one FPGA+ADC demo-board project from a major ADC company, where the gated clock output for the serial data transfer is implemented incorrectly in the provided example FPGA logic. The flawed clock-forwarding (and lots of other problems) results in the first serial clock-pulse to the ADC being narrower than the rest. Strange data resulted, until I re-wrote the VHDL code.

 

Best regards

 

 

 

 

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Visitor anirban1988
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7,678 Views
Registered: ‎08-20-2014

Re: BRAM behaving oddly

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The data from the ADC is always correct as I am keeping track of the data on an oscillocope. Its only when I am reading the stored data from memory that I am seeing an extra bit.

Is it a behavior of the BRAM itself? I can't find anything in the user manuals.
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Visitor anirban1988
Visitor
12,862 Views
Registered: ‎08-20-2014

Re: BRAM behaving oddly

Jump to solution

Looks like it was some error in my control logic for the data reading process. I completely rewrote my logic generation and the problem is solved.

0 Kudos