Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

jtag uart speed problem

Status
Not open for further replies.

dipin

Full Member level 4
Joined
Jul 16, 2014
Messages
223
Helped
14
Reputation
28
Reaction score
14
Trophy points
18
Activity points
1,731
hi,


i am using JTAG UART fro quartus qsys system to print some values from fpga to nios 2 terminal. the register (32 bit) inside fpga updating at a rate of 10khz,and i am using a clock of 50 mhz to qsys system(to jtag uart). problem is printing every 4th values, in between 3 values are missing .i believe that its the problem of max through put of jtag uart.is there any way i can print all the values, ie did jtag uart can output a 32 bit register at 10khz ?

i am using cyclone 5 soc kit

thanks and regards
 
Last edited:

Assuming the default JTAG clock frequency is 6 MHz like the Xilinx JTAG pod, then to continuously transfer the 32-bits alone with no overhead is 6000000/32 = 187500. Given there is a lot of overhead in the JTAG UART of Xilinx, I'll assume the same is true for the Altera one, I kind of doubt that a factor of 18.75 is enough overhead to transfer the register at 10KHz. If your running the JTAG at even a lower frequency then 6MHz, then the 18.75x overhead is even lower.

Given that you have a clock domain crossing from the 50 MHz qsys to the JTAG UART will eat into your performance. Along with the conversion from the 32-bit register to a ASCII output over the UART (so it can be displayed) I can easily see you ending up with something more than an order of magnitude worse performance than raw 32-bit serial transfers at a 187.5 KHz rate.

Xilinx's VIO JTAG update rate is pretty darn slow for status signals and/or the internal ADC temp and voltage sensor. Even at the highest rates it doesn't look like much more than 10's of Hz. JTAG overall is a pretty overhead heavy protocol, so you shouldn't expect much performance. You would be better off not using the JTAG UART and using a UART directly connected to your register logic, which is then connected to some UART-USB dongle on your PC.
 
  • Like
Reactions: dipin

    dipin

    Points: 2
    Helpful Answer Positive Rating
Status
Not open for further replies.

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top