Lpc2000

The JTAG is disabled on reset and it is enabled by the bootloader code 
when CRP is not enabled. See previous discussions on this list about 
JTAG debugging from reset for more information.

Richard.


jayasooriah wrote:

> Am I right in assuming LPC2000 CRP is a software fence implemented in
> the supplied boot loader code?
>
> In the case of AVR, CRP is implemented in hardware.  This means that
> locked down code in flash can be executed but not read from flash by
> preying eyes.  Thus we ship products with our code locked down in the
> boot sector assured that our code is secure from preying eyes.
>
> If JTAG is used to bring LPC2000 out of reset on power up (and thus
> stop boot loader code from executing), will this also void CRP?
>
> The LPC2000 series support Quick-Pulse programming.  Can this method
> of parallel programming be used by preying eyes to read CRP'ed code?
>
> --- In lpc2000@yahoogroups.com, "philips_apps" <philips_apps@y...> wrote:
> >
> > Hello Jayasooriah,
> >
> > Code Read Protection (CRP) was implemented with intention to protect
> > on-chip Flash content from preying eyes.
> >
> > In context of a system with external memory, this means that
> > external memory components can be used, but in that case LPC2000
> > with enabled CRP cannot boot from external memory.
> >
> > Once LPC2000 starts executing user's code it does not care if the
> > code is on or off chip, as long as fetched op-code is valid. If a
> > LPC2000 device would have CRP enabled and booting process would
> > direct code execution to an application in external memory, there
> > would be no way to protect on-chip flash content from being read by
> > such application.
> >
> > However, having CRP enabled in a system with external memory and
> > booting from on-chip flash is perfectly valid scenario. As long as
> > LPC2000 is not fetching any executable code from external memory,
> > CRP will accomplish what it is designed for. This is the case when
> > external memory is used for data storage only.
> >
> > All in all, the moment an off-chip located code is fetched, CRP's
> > role is voided.
> >
> > Regards,
> >
> > Philips Apps Team
>
>
>
>
>
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