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Nuno137

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02-22-2021 01:59 AM

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Registered:
02-22-2021

Hello, I have a very simple question. There is no info about this simple thing in the documentation. I can't test this with my board so that's why I ask you.

I need to use a DSP48 to implement a 48bit wide boolean function, like an AND or a XOR. Usually the AND of N bits is just the product of all boolean variables, so it is zero if at least one variable is zero, and one if all variables are one.

In the DSP48 *I assume* this is not the case, considering the output is still a 48 bit wide signal, and it is not a 1 bit signal. The AND of these 48 bit input signals, X AND Z, is the 2bit AND of the corresponding bits? For example assuming the signals are 6 bits wide:

010110

AND

110101

=

010100

Is this right? Does the DSP actually do this?

Thanks.

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bruce_karaffa

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02-22-2021 03:37 AM

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4 Replies

markg@prosensing.com

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02-22-2021 02:50 AM

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01-22-2015

The DSP48 is used to do many things as described in the following document.

https://www.xilinx.com/support/documentation/ip_documentation/dsp_macro/v1_0/pg323-dsp-macro.pdf

However, the DSP48 is not used for boolean operations.

When you use boolean operations in your HDL, they will be implemented using circuit blocks in the FPGA called Look Up Tables (LUTs).

Cheers, Mark

Nuno137

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02-22-2021 03:05 AM

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02-22-2021

In this guide: https://www.xilinx.com/support/documentation/user_guides/ug479_7Series_DSP48E1.pdf

In "Embedded Functions/Two-Input Logic Unit" it says that I can perform also basic functions. There is also a list of possibile functions. I want to use this, and I'm not interested in the multiplication/addition capabilities of the DSP48. In the list there is for example the function "X XOR Z" or "X AND NOTZ". What I want to know is what these actually do.

I know it is not intended as so, and DSP48 should be used for things like FFT or audio processing, filters and so on, but I may need to save resources and so I may be interested in using the DSPs.

bruce_karaffa

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02-22-2021 03:37 AM

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Nuno137

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02-22-2021 03:41 AM

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Registered:
02-22-2021

Thanks both for the replies, much appreciated!