Communication Loss

We are currently using a TMS320F2806x Chip running a C program on a breakout board that connects to 6 channel motherboards. We use a LS PLC to communicate to the Chip using RS485. The PLC communicated with up to 6 chips (6 channels) at a time. The communication intervals are currently running at 200ms, this is to slow. But once we change the intervals to 100ms, the data received from the cards are incorrect and the comms drop away. But this is also something random that some cards work and other don’t. Along with this problem we have noticed problems in the returning packets from the chip using the PLC Frame Monitor. What we have also picked up is in some cases when the weather is cold some chips don’t start either.