JTAG UART dyslexia

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originally posted by bigboss25@Jan 28 2007, 02:17 PM

hi all,

i made a very small design and i got some problem with the jtag uart terminal output. i compiled a simple "hello world" and everything works fine excepted that jtag uart is "dyslexic" : instead of "hello world" i get "hhello world" in the jtag uart console.

anybody can help ?

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Well, I found the solution, but I don&#39;t know why it works ... http://forum.niosforum.com/work2/style_emoticons/<#EMO_DIR#>/mad.gif

Originally my master clock was 12 MHz, including JTAG UART. Then I changed only the JTAG UART input clock to 50 MHz... and it works . Strange. Is there something hard coded into JTAG UART which need a clock faster than 12 MHz ?

Yes.... The SOPC Builder system clock has to be greater than twice the maximum JTAG clock. Depending on what download cable you&#39;re using, you might see up to 10MHz on the JTAG clock.

- slacker

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originally posted by slacker@Feb 1 2007, 06:57 AM

yes.... the sopc builder system clock has to be greater than twice the maximum jtag clock. depending on what download cable you&#39;re using, you might see up to 10mhz on the jtag clock.

- slacker

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Brilliant http://forum.niosforum.com/work2/style_emoticons/<#EMO_DIR#>/tongue.gif

Works fine at 25 MHz now. Thx

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originally posted by slacker@Feb 1 2007, 06:57 AM

yes.... the sopc builder system clock has to be greater than twice the maximum jtag clock. depending on what download cable you&#39;re using, you might see up to 10mhz on the jtag clock.

- slacker

<div align='right'><{post_snapback}> (index.php?act=findpost&pid=21112)

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Is there a way to slown down the JTAG clock (let&#39;s say downto 5MHz) via software option or does it only rely on my PC hardware?

Thx.

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originally posted by bigboss25+feb 3 2007, 04:16 am--><div class='quotetop'>quote (bigboss25 @ feb 3 2007, 04:16 am)</div>

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<!--quotebegin-slacker@Feb 1 2007, 06:57 AM

yes.... the sopc builder system clock has to be greater than twice the maximum jtag clock. depending on what download cable you&#39;re using, you might see up to 10mhz on the jtag clock.

- slacker

<div align='right'><{post_snapback}> (index.php?act=findpost&pid=21112)

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Is there a way to slown down the JTAG clock (let&#39;s say downto 5MHz) via software option or does it only rely on my PC hardware?

Thx.

<div align='right'><{post_snapback}> (index.php?act=findpost&pid=21179)</div>

[/b]

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Unfortunately no; I believe its actually a function of the download cable (USB Blaster, etc.). I could be wrong on this one, but I seem to remember that if you have access to an older cable (byteblaster, parallel port cable) this may have a slower Tck (JTAG clock) frequency.