Using the internal 400 kHz oscillator as clock for the P89LPC935

[John Poore]

The microcontroller I am using is the Philips P89LPC935.

Using Flash Magic and the Keil MCB900 board, I select "Watchdog Oscillator (400 kHz +- 10%)" as the Clock source in the UCFG1 popup then click "Reprogram" on that popup, it is not programmed and I can never communicate with the microcontroller again.
 
I have tried selecting the internal 400 kHz oscillator as clock in 2 different microcontrollers. Both are now non-programmable.
 
How do I use the 400 kHz clock as the system clock?

[Andy Ayre]

Because 400kHz is very slow, the baud rate you use also has to be very low to match. I tested using the LPC935 on an MCB900 board clocked from the Watchdog oscillator and found that I could connect only at 600 baud. To use this speed you will need to directly enter "600" into the Baud Rate box in section 1 of the Flash Magic window. The value in the Oscillator Frequency box is not used so can be anything.

Let me know if this solves your problem.

[John Poore]

Yes, Andrew's suggestion works. Thank you Andres