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Altera_Forum's avatar
Altera_Forum
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15 years ago

jtag_uart bitrate

Hi,

what is the theoretical maximum bit rate for jtag_uart ip in sopc? assuming no other IP is using the usb-blaster cable.

currently I'm sending data from NiosII to computer using jtag-uart and jtag-atlantic. however I need to know the exact bit rate.

Thanks

Adel

3 Replies

  • Altera_Forum's avatar
    Altera_Forum
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    15 years ago

    thanks for your prompt response.

    I tried to push jtag-uart to see if I could squeeze any more bits out of it.

    at best, it gives around 150-160KB which is equals to 1.2-1.3 Mbps.

    it's roughly 80% utilization of usb-blaster cable considering the bandwidth of USB 1.0 is ~1.5Mbps. (usb-blaster is usb1, right?)

    Nios2/f is clocked at 150MHz on a cyclone III fpga (sg=2). jtag-uart has 1k buffer.

    also all ip-cores that might use the usb-blaster (like signal tap) are turned off.
  • Altera_Forum's avatar
    Altera_Forum
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    15 years ago

    USB Blaster is uses Full Speed USB (FTDI FT245), but the JTAG speed is limited to 6 MHz by the USB Blaster Hardware. Furthermore there is a considerable overhead of the virtual JTAG protocol transferring the UART payload with a word length of 8-Bit only.