ARM7/LPC21xx debugging capabilities

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Hello All,

reading some of the specs I'm still not completely sure about the
debugging capabilities of a LPC21xx.

Can I access memory "non intrusive" while the program is executing
(like BDM in the 68HC(S)12 or the HCS08?)?

Or does a memory read always interrupt program execution for some

If "non intrusive" is possible: is this a standard feature of

Any general hints about good debuggers?

Links to web sites about this topic also welcome.

Thanks in advance,

Oliver Betz, Muenchen (

Re: ARM7/LPC21xx debugging capabilities

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It depends? If you are using JTAG, I think you are access memory while
the program is running. If you are using a monitor, then no.

// richard

Re: ARM7/LPC21xx debugging capabilities
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Have a look at /

or post your question there. There are a lot of experts which (i think) can
help you !



Re: ARM7/LPC21xx debugging capabilities
Hi Oliver,

the LPC21xx has two debugging interfaces. One is called JTAG and
allows most things that BDM can do. This is supported by many
debuggers, such as Keil, IAR, ... but also by the emulator vendors
like Nohau, Hitex, Ashling (and many others) support this device via
JTAG and the second option which is called ETM (embedded trace
macrocell).  This option allows real-time, non-intrusive codetrace.
ETM requires an additional 9 pins which will not be availble for I/O
if you use them for debugging. By the way, it seems that Philips is
more serious about debugging options than e.g. Atmel or ST
Mircoelectronics with their ARM7 devices. All three offer JTAG but
only Philips offers trace capability with ETM. For more questions
about the LPC2000 family the user group in Yahoo is an excellent
source of information. You can find it here: /

Greetings an Schwob in the US
p.s. comparing the LPC21xx to the HCS08 is like comparing a BMW
5-series M to a Ford Taurus (similar to a Mondeo in Europe). Both are
similar in size and can transport 5 people but the performance is VERY
different. Luckily the price difference in the microcontrollers does
not exist if you compare similar memory sizes.

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Re: ARM7/LPC21xx debugging capabilities

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but I didn't find any information about accessing memory during
program execution.


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hmm, 9 additional pins is pretty much. But I need only variable access
most times.


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I will ask there.

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certainly, I only wanted to compare the debug interface capabilities.
The LPC21xx could be an alternative to the HCS12 I'm using at the

The Motorola BDM background memory access is a really nice feature in
small embedded applications, because I can watch the state of my
program without debug code (well, maybe make some variables global).

BTW, I never used a HCS08, only HC08 (cheap, small) and HC(S)12
because a HCS12 has a better performance/price ratio.

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hmm, too much software in modern cars. Could be I have to buy a Lada
next time <g>.

Oliver Betz, Muenchen (

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