NI PXI-7853R Block Memory

[ChristophHS]

Dear all,

how do I configure a maximum sized Block Memory on my FPGA Target and what is the allocated memory size?

The Documentation states:

NI PXI-7853R  : On-Board Memory 384 kB

Short Specs : Embedded block RAM 3,456 kbits

384 kB = 393216 Byte

3456 kbit = 432000 Byte

What's the deal here?

Configuration Dialog for Memory in FPGA Project

Datatype U8

"Requested number of elements" : max. 4294967295 (Value stays even if higher value is entered, seems to be a 32bit overflow)

Actual number of elements: 134217728 (no Idea what this number means).

I am simply assuming 393216 or 432000 is the max. number of Bytes I can enter?

Eventually there is a build error (xilinx error) regarding the ram size if the number is higher.

However if there's no error (eg using 393216) the build process (usually 10 minutes) does pass "generating xilinx ip" within 15 minutes .

I don't want to continue guessing, so what is the number I enter in the Memory Configuration Dialog for max. Memory ?

Regards

Christoph

[Duffy2007 · Accepted solution]

Hello ChristophSauter,

The maximum number of elements that can be created in one FPGA Memory item for the PCIe-7854R card when using U8 is between 442368 Elements and 393216 Elements depending on the optimizations the Xilinx LogiCore Block Memory Generator Minimum Area Algorithm can make.

The Embedded Block Ram is 3456 Kbits -> 3538944 bits

But it is importand to know how many block ram blocks are a available and which data you want to write into the memory it could be that the 8bit of data use 9bit in the memory . Virtex-5 Family Overview page 2 XC5VLX85 is the FPGA and the information about this.

Hope this helps.