Re: [Openocd-development] adapter_khz ...

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

David Brownell wrote:
> On Wednesday 24 March 2010, Laurent Gauch wrote:
>   
>>> We really don't want to need JTAG and SWD versions of every config
>>> script and event handler based on what transport is in use...
>>>   
>>>       
>> We do not need to write specific scipt versions for JTAG or SWD serial 
>> port, but we will have to give in the target script what is the maximum 
>> specific frequency of each serial port :
>>
>> 'target_jtag_max_tck_frequency_khz'
>> 'target_swd_max_tck_frequency_khz'
>>     
>
> JTAG and SWD share key signals though ... on both adapter and target
> sides.  Lots of boards have a single JTAG/SWD connector.
>
>
>   
Yes, lot of boards, but not all boards. Amontec has customers having 
JTAG daisy chains of more than 10 devices (target) on the same boards.

Also, that's why we have target script and board script. At board level, 
if you have 3 targets in the JTAG chain, with max frequency of 15MHz 
30MHz 60MHz, the max frequency of the JTAG chain will be around 15Mhz. 
Also, this is why we have max frequency specified in the JTAG BSDL file. 
But not all targets comes with BSDL. Result, we have to specify JTAG max 
frequency to any target script.

SWD cannot support more than one device on the same port !
JTAG + RTCK is actually not really used in JTAG daisy chain structure.

Laurent
 http://www.amontec.com

> I really see *NO* good things coming from creating more ways to confuse
> configurations.  Especially .... more *needless* confusion.
>
>