Hi Peter,
Thanks for your comments, Both the Slaves and Masters are my design so I have control over the inter frame delay. Indeed the uTasker module has a define to control this specific point.
My questions are related to the specific way the uTasker Modbus module works, from my tests it looks like the Timeout you specify in the modbus parameters, starts from the point the first character is transmitted, rather from when the last character is transmitted. The problem with this is that I may have a very short message where a short time-out would work, but I may also have a large message which also has a large reply which would need a longer time-out.
You can see from the attached trace where the time-out is set at 10ms the time-out seems to be based on the start of transmission, the inter message gap is only 7ms.
My other worry was again with a short inter message time-out and receiving a large packet of data, would the time-out kickin in the middle of the packet being received?
I'm fixed with using RTU comms for other reasons.
Cheers
Martin