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nadaumtimuj
Adventurer
Adventurer
348 Views
Registered: ‎01-29-2021

Slow JTAG read

What is the optimum frequency for AXI master-slave when the system clock frequency is 250 MHz and JTAG frequency is 15 MHz? Thanks..

I currently set it to a clock_out of 200 MHz which seems to be very slow when I do read write. I am using KCU040 board and using a micro USB cable that connects to Digilent USB JTAG module on the board.

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drjohnsmith
Teacher
Teacher
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Registered: ‎07-09-2009

The JTAG and the AXI are not directly related

The JTAG can run at say 1 MHz or 10 MHz, the AXi does not care.

 

JTAG is used for debug and configuration, not real time access.

  It runs over a serial link, similar in many ways to SPI, 

        https://www.xjtag.com/about-jtag/design-for-test-guidelines/

 

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nadaumtimuj
Adventurer
Adventurer
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Registered: ‎01-29-2021

@drjohnsmith Thanks! I am using JTAG for read/ write through MATLAB. I have implemented this design here:


Access FPGA External Memory Using MATLAB as AXI Master - MATLAB & Simulink Example (mathworks.com)

Instead of external memory, I am just writing to slave register.

 

So you are saying whatever I am getting is my bottleneck? I can read 10k samples in 20 sec with a 15 MHz JTAG connection.

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drjohnsmith
Teacher
Teacher
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Registered: ‎07-09-2009

thats not bad speed for  a serial link,

   I'm amazed your getting 15 MHz reliably

       JTAG is normally a few MHz, they must have made that board for speed.

dump Matalb might speed things up somewhat 

  but thats a different story

 

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nadaumtimuj
Adventurer
Adventurer
303 Views
Registered: ‎01-29-2021

Not sure if I am getting truly 15 MHz. But both Matlab and Vivado shows that my connection speed is 15MHz. All I know is I can perform 10k read operations (10k MATLAB readmemory function)  in 20 sec. Thanks anyway!