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K66 RMII clocked on EXTAL0

Question asked by Ian Wilson on May 17, 2016
Latest reply on Feb 27, 2017 by ishwarlal

Hi all,


We are tearing our hair (what is left of it) out with a issue on a K66 - the RMII port is not pushing data to our PHY.


We have a K60 on a custom board that is loosely based on the TWR-K60F120M - same RMII pin allocation, same clocking (50MHz external oscillator on EXTAL0 and 12 MHz crystal on EXTAL) and same phy (Micrel KSZ8041NL). We decided we needed more RAM so have done a careful due diligence on pin function compatibility. Now we have removed some K60 and replaced with K66.


Now we are working on porting the code.  From our detailed comparison of the user manuals we were not expecting a big issue. And most was easy.  Ethernet is not working though.


We need to operate the RMII from the external 50 MHz signal on EXTAL0 (pin 72).  We have set SIM_SOPT2[RMIISRC]  to 0. The ENET module clock is enabled.  The ENET register settings are the same as our K60 build. Yet we see nothing on the RMII_TXEN signal on the K66 (we do see the expected pulse on the K60).


MQX RTCS_init goes through just fine (no error) and when we trace through the code the initial ARP_send function does not return any error. Reading back the phy registers through the MDIO channel shows all as expected (and this wouldn't stop the RMII_TXEN signal from behaving anyway).


It is as though we are not clocking the RMII peripheral.


Does anyone have any useful thought?


Many thanks in advance,