Re: [OpenOCD-user] LPC1857 reset problem

[Dominic R. <Dom...@gm...>]

Hello Paul,

On 19.04.2015 20:01, Paul Fertser wrote:
> still get some errors.
>> After playing around with reset_config for a while, I found out that
>> reset_config trst_and_srst srst_pulls_trst allows me to reliably reset
>> the board, even if I reenable above commit.
> Can you check if it's a board's limitation or rather a target's and
> hence the upstream LPC1850 config should be modified accordingly?
>
The board connects SRST straight to the processor's /RESET,
and TRST goes right to the processor's /TRST, no connection
between the two lines.

The LPCs always used to be special with regard to reset, because
of their "Code Read Protection" - you write a certain signature to
a location in the internal flash, and that disables JTAG and removes
some features from the ISP bootloader (e.g. only full erase possible).
 From what I found out back then is that JTAG really comes up disabled,
and only gets enabled by the ROM code if the CRP signature isn't set.
I think it was for the LPCs that we first implemented srst_pulls_trst.

I'm really not sure any more if this is a restrictions that affects
all LPCs, since I found this thread
http://sourceforge.net/p/openocd/mailman/message/28345948/
where Peter Stuge posted a patch to remove srst_pulls_trst from his
LPC2148, because he didn't find it necessary. He even wrote that he
was able to 'reset halt', which is something I always thought
impossible with the LPCs.

Regards,

Dominic