External Clock input on LPC 936 - How to connect Flash Magic?

[Tilo]

Hi!

I configured my LPC936 to use an external Clock on xtal1.

My question is, how is it possible to connect Flash Magic for reprogramming?

Thanks for help!

[Andy Ayre]

Did you change the clock setting in UCFG1 via ISP before switching clock sources? What crystal frequency and baud rate are you trying to use?

[sololf21]

i have the same problem too, cant connect to flash magic.

I've tried to change the configuration of the external crystal using ISP/Device Config/Clock/Options choosing external high frequency clock but the error i received was "unable to connect at the specified baud rate, try reducing the baud rate, reset the hardware into ISP mode again". apparently, every setting we have changed results in this error message.

I've also tried to send the "U" command using the bootloader and the error message was "operation failed. (start bootrom command - no echo)

i also had nxp to check out my schematics and they mentioned that it is okie.

pls help 

[Andy Ayre]

Have you put a scope on the XTAL pins to see if there is a sine wave?
Was your hardware/device/cable/PC working with Flash Magic when you were using the internal oscillator or did you not try that?
Try putting your scope on the RxD pin and check the 'U' is arriving. Then put it on the TxD pin and see if the 'U' is being echoed back. If it isn't then the device is not entering ISP mode.

Double check how you are placing the device into ISP mode using your scope.

Andy

[Je Gold]

Flash magic uses... 3pulse on reset method with the command and programming data sent to the RxD / TxD UART pins of the micro.

The UART requires a stable/reliable Osc...

If you have reconfigured the Oscillator configuration non-volatile  selection  then  you should get the micro oscillator operating in this mode, as the UART is Dependant on oscillation from the selected - reliable source.

So that may mean putting a Xtal or Osc and Osc-caps on Xtal1 Xtal2 pins of the micro to get it oscillating in the correct mode, programming the part and selecting the correct Osc input.

===> Otherwise the brute force method is to use ICP which programs the micro at a lower hardware level where the Osc is not required.


Joe

Joe