LPC1788 cannot write to CAN1CMR

[lpcware]

Content originally posted in LPCWare by tetwin11 on Mon Sep 23 09:31:34 MST 2013
I'm trying to get the CAN peripheral up and running on a LPC1788, but I've hit a snag.
In the send function, I'm writing to CAN1CMR to request a transmit

CAN1CMR = CAN_CMR_SET_TX_REQUEST | CAN_CMR_SEL_TX_BUFF_1|CAN_CMR_SELF_RECEPTION;

But it doesnt seem to be doing anything. In the IAR Embedded Workbench, I can write directly to CAN1CMR while debugging and the transmission does seem to occur.
Why can't I write to CAN1CMR during normal operation????
Thanks
Matt