Rockwell Automation 900-TC32 Digital Temperature Controllers, Series B - Manual (Page 349)

Publication 900-UM007D-EN-E - January 2011
Troubleshooting & Error Indication 6-9
The host device sent another command
before receiving a response from the Controller. The response must always be read after sending a command (except for
broadcast commands).
The host device sent the next command too
soon after receiving a response from the
Controller. After receiving a response, wait at least 2 ms before sending the next
command.
The communications line became unstable
when Controller power was turned ON or
interrupted, and the host device read the
unstable status as data. Initialize the reception buffer in the host device before sending the first
command and after turning OFF the power to the Controller.
The communications data was corrupted
from noise from the environment. Try using a slower baud rate.
Separate the communications cable from the source of noise.
Use a shielded, twisted-pair cable for the communications cable.
Use as short a communications cable as possible, and do not lay or loop
extra cable.
To prevent inductive noise, do not run the communications cable parallel
to a power line.
If noise countermeasures are difficult to implement, use an Optical Interface.
Table 6.B
Meaning Countermeasures