Øyvind Harboe wrote:
I don't subscribe to the idea that there is a safe, correct and robust
default setting for JTAG clock, better to make the user get a
good error message that points him in the right direction.
1MHz will fail on plenty of cards (with RC oscilators typically).
I do not say the 1MHz is safe correct and robust, but having a known
1MHZ JTAG at startup, is is a good way to let the user do something with
openocd without having to obligatory set a specific frequency in the
script. If the 1MHZ failed, it failed ... and something specific must be
present in the script.
Xilinx Altera Actel do in this way.
THE SAFE CORRECT ROBUST frequency can never be known as static ! A good
JTAG software has to find this frequency by itself (auto-detecting the
max safe JTAG frequency );-)
Too many parameters are around THE SAFE CORRECT ROBUST frequency ;-)
---
True regarding the cards with RC oscillator starting at super low
frequency as 30KHz, but it is already specific to a target.
In this case the 1MHZ should not let to find and detect the chain and we
report a error message.
The default frequency could be 10KHz instead 1MHZ ...
But to set a default frequency at the JTAG API level and at startup is
to fix something (something good or not, but FIX).
Laurent
http://www.amontec.com
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