Is it possible to send regular periodic messages using the Fastcomm 422/2-PCI-335

I have a setup where a target machine running xPC Target 5.5 is acting as a master on an RS-485 databus using the Fastcomm 422/2-PCI-335 card and the Unit Under Test (UUT) is the slave. The UUT will only respond when spoken to.

It appears that the message transmission is tied in with the sample time of the block in the model and as such sends a message every time the code for that block is executed. Because the TET of the code is variable, if, for whatever reason, the code runs slowly in one frame and quickly in the next and the code for the transmission occurs at the end, the two send messages from the target machine can occur in such quick succession that the UUT does not have time to respond in between causing message clashes on the wire.

Ideally I would like to send a message every 0.521ms to a reasonable degree of accuracy.

I have masked this issue for the moment by assigning the block a high priority and so it executes earlier on the code and thus is subject to less variation. However, this is purely a mask and not a fix.

Any help would be greatly appreciated.

Thanks,

Kevin Heaton, Lead Systems Engineer, GE Aviation Systems.