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Altera_Forum's avatar
Altera_Forum
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20 years ago

JTAG UART Gotcha...

I've just been bitten by the JTAG UART hanging my system when the USB cable was disconnected.

I'd read about the dangers of the 'small' mode, and I have a valid system clock timer, etc..

But, it turns out my problem was the order of the JTAG UART vs. SYS_CLK_TIMER in SOPC builder - the UART was trying to initialise before the clock, so it's call to alt_alarm_start was failing silently, and the timeout procedure never gets called...

Easy to fix, but a pain to track down... http://forum.niosforum.com/work2/style_emoticons/<#EMO_DIR#>/sad.gif

- Roddy

2 Replies

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    20 years ago

    What do you mean by &#39;order&#39;. I thought device init order was canned - so how did you fix it?

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    20 years ago

    Devices are initialised in the order they appear in SOPC builder, so you use the &#39;move up/move down&#39; buttons to place the clock above the JTAG UART. alt_sys_init.c will then get rebuilt to reflect this new ordering.

    - Roddy