Lpc2000

Hello Søren,

Not sure what processor you are using but I think you are diabling the JTAG by changing a JTAG line into a GPIO line.

I am using the LC2129 and the usermanual of this processor shows the following:

Table 63: Pin Function Select Register 2 for LPC2119/2129/2194
(PINSEL2 - 0xE002C014)

1:0 Reserved.

2 When 0, pins P1.36:26 are used as GPIO pins.
   When 1, P1.31:26 are used as a Debug port. (RTCK)

3 When 0, pins P1.25:16 are used as GPIO pins.
   When 1, P1.25:16 are used as a Trace port.  (TRACESYNC)

4:5 Reserved.  Note: These bits must not be altered at any time.
     Changing them may result in an incorrect code execution.

6:31 Reserved.

According to this info you are disabling the JTAG RTCK line.

Hope this helps,
Aalt

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Aalt Lokhorst
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soren_t_hansen wrote:
> I'm trying to write to the PINSEL2 register, to ensure that it has 0's
> at bit 2 and 3, but if I try to write to the register, the JTAG
> connection drops, and it seems as if the MCU enter some other mode,
> since I can't restore the connection whitout having to do a power cycle.
> Has anyone experienced this?
> And how can I write to the PINSEL2 register, whitout having this problem?
> > /Søren
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