Rockwell Automation 900 Temperature Controller Communications Functions - Series B - Manual (Page 76)

Publication 900-UM004D-EN-E - July 2010
4-18 Modbus Communications Procedure
Operation Commands and Precautions
• Communications Writing
Set the Communications Writing parameter to “ON” (enabled) or
“OFF” (disabled) with the related information setting. The setting can
be accepted in both setup area 0 and setup area 1. An operation error
will occur, however, if communications writing enable/disable is set for
an event input.
• RUN/STOP
Set control to “run” or “stop” with the related information setting. The
setting can be accepted in both setup area 0 and setup area 1. An
operation error will occur, however, if RUN/STOP is set for an event
input.
• Multi-SP
Set four set points beforehand in the adjustment level so that you can
switch to a desired set point. The setting can be accepted in both setup
area 0 and setup area 1. An operation error will occur in the following
situations.
– When AT is being executed.
– When the Multi-SP Uses parameter is set to OFF.
– When the Multi-SP Uses parameter is set to ON but multi-SP is set
for an event input (Number of Multi-SP Uses > 0).
• AT Execute/Cancel
Set AT (auto-tuning) to “execute” or “cancel” with the related
information setting. This command can be accepted in setup area 0 only.
An “operation error” will be generated in the following instances:
– When the RUN/STOP parameter is set to “stop”
– When the command is executed in “setup area 1”
– When ON/OFF control is being used
– When 40% AT is specified during 100% AT execution.
– When 100% AT is specified during 40% AT execution.
In addition, a parameter error will occur if 40% AT execution is
specified during heating and cooling control.
Note: If the same type of AT execution is specified during AT execution
(e.g., if 100% AT execution is specified during 100% AT execution), the
AT will not be restarted and the operation will end in normal
completion with no processing.
• Write Mode
Set either “backup mode” or “RAM write mode” with the related
information setting. The setting can be accepted in both setup area 0
and setup area 1.
The number of EEPROM (non-volatile memory) write operations is
limited. Therefore, use RAM write mode when frequently overwriting
data.