How to send a LPC921 into ISP with USB?

[BigGuy26]

I want to be able to send my LPC921 into ISP mode using a USB cable, but I do not want to add another micro to the board.  Will just calling the the boot loader (by setting the Boot Status bit) when voltage is detected on the USB line work?  Right now I plan an input pin on the LPC921 connected to the USB device.  If there is a better way, please tell me.  Thanks.

Brian

[Andy Ayre]

you can use IAP to set the Status Bit and then use the watchdog to timeout. You could also use a USB to RS232 cable.

[BigGuy26]

Thanks fo the advice.  Can I use the IAP Lite to write 0x01 to the status bit  If so, what is the address of the status bit?  (Sorry, I am new at this)
Thanks