Re: Use of TRST on ST vs. Luminary ARM JTAG?

On Feb 10, 10:10 pm, Tim Wescott <t...@xxxxxxxxxxxxxxxx> wrote:
I'm using an ST ARM Cortex part for the first time.  I've been using
Luminary parts until now.

I notice that on the Olimex demo board for the STM32F103RBT6, they have
the JTAG TRST pin connected,

Good idea, since you want the CPU reset/halted while programming the
flash.

but on the Luminary eval board for the
LM3S811 the TRST pin is left open.

Does anyone know why this is?  Is it just that the TRST pin is sorta
optional,

Yes, it should be optional. Jtag I/O chains should not be affected by
CPU state.

and the Luminary folks weren't in a mood to dot all their 'i's
and cross all their 't's?  Is there some reason that you might _not_ want
to connect TRST?

Saving a port/pin?


I also see that the Olimex board has a solderable bridge to connect TRST
to the processor reset.  Again -- why, do you know the advantages and
disadvantages?

Not a good idea. Processor reset is usually tied to high capacitive
load. That's probably not good for the debugger driver.


I'm going to just copy the Olimex board, but I'm curious as to just what
it is that I am so blindly doing...

--
My liberal friends think I'm a conservative kook.
My conservative friends think I'm a liberal kook.
Why am I not happy that they have found common ground?

Tim Wescott, Communications, Control, Circuits & Softwarehttp://www.wescottdesign.com

.

Relevant Pages

  • Use of TRST on ST vs. Luminary ARM JTAG?
    ... LM3S811 the TRST pin is left open. ... I also see that the Olimex board has a solderable bridge to connect TRST ... My liberal friends think I'm a conservative kook. ...
    (comp.arch.embedded)
  • Re: Use of TRST on ST vs. Luminary ARM JTAG?
    ... LM3S811 the TRST pin is left open. ... I also see that the Olimex board has a solderable bridge to connect TRST ... The Keil Ulink interface supports JTAG and the ARM SW debug interface. ... Keil suggest connecting the reset pin which can be used to reset the processor from the debugger. ...
    (comp.arch.embedded)
  • Re: Use of TRST on ST vs. Luminary ARM JTAG?
    ... I notice that on the Olimex demo board for the STM32F103RBT6, ... the JTAG TRST pin connected, ... LM3S811 the TRST pin is left open. ... Processor reset is usually tied to high capacitive ...
    (comp.arch.embedded)