Daniel Zahner

CPM command register - spurious command execution??

Discussion created by Daniel Zahner on Jan 8, 2008
Latest reply on Jan 16, 2008 by Paul Genua
Anyone with experience with Quic - CPM command register.  We seem to be observing some strange behaviour.   We set up the MPC860T communications (SCC1,SCC2, etc) we are also using SMC2 as a UART.  Everything is fine.   The very last command to the CPCR is Init RX and TX params on SMC2.
 
 
The unit will run for days, then the SMC2 uart behaviour becomes erratic.  We have found the cause to be that during operation the Init TX and RX params command is resent to the CPM.
 
Our core is not resending this command (by setting the FLG bit), but the command still remains in the CPCR opcode and channel register as a leftover from the initialization at powerup.   It seems the CPM is somehow fooled into reprocessing this command.
 
We thought that by setting the opcode and channel to a benign operation like close Rx buffer SMC2 might resolve the problem for us, since SMC2 is a TX uart only.   We have found that sending this command repeatedly during run mode has no ill effects.  
 
Does anyone else have experience with leftover commands suddenly being executed by the CPM?
Are there other consequenses that we are not considering? 
 
Thanks

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