Re: [Openocd-development] Getting rid of default jtag clock rate

[Laurent G. <lau...@am...>]

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