USB ISP mode without external crystal?

Discussion created by lpcware Employee on Jun 15, 2016
Latest reply on Jun 15, 2016 by lpcware
Content originally posted in LPCWare by Dmaroto on Thu Aug 13 04:28:03 MST 2015
I am trying to use the USB ISP mode to program an application for the first time and the micro (LPC1547) does not seem to enter into USB ISP mode.

I have checked the voltages and states of ISP_0 and ISP_1 during power up and all seems to be as it should.

I did see this note in section 5.4 of the user manual:

Remark: In USB ISP mode, an external 12 MHz crystal is required  to communicate with the external storage device. (I did not consider the chip Flash as "external" when designing the circuit).

Can the LPC1547 actually start in USB ISP mode without an external clock?

Thank you for your help.