Why I can not access ISP mode again?

Discussion created by lpcware Employee on Jun 15, 2016
Latest reply on Jun 15, 2016 by lpcware
Content originally posted in LPCWare by allankliu on Sat Dec 14 02:49:27 MST 2013
I have a mini board for LPC812M101JD20 (SO20, but not FD20). The attached PDF is its schematics. In this schematics, CP2102 was used as USB/UART bridge, two buttons (ISP/RST) are used to enter ISP mode to download the hex code via Flash magic software.

Currently I haven't populate onboard CP2102, but using an external PL2303. And I didn't populate 12MHz crystal as well, since I think IRC will be used during ISP anyway.

By pressing and releasing RST while holding ISP key, I can enter ISP mode and program hex code. However I can not enter ISP mode later with same actions.

Do I miss anything to enter ISP mode again?

Looking for quick suggestions, since I have already put them on production plan. I am going to use it as a mini-dev-kit for Android USB host application.