RXT-300 SmartWireless™
RXT-300 Wireless IM
Rev. 2.0
Page 29 of 41
5.2.1
Modbus™ Exceptions
The RXT-300 is capable of returning Modbus™ exceptions when it cannot service a Modbus™ request meant
for that RXT-300. By default this is turned off in the configuration since it can cause issues with some
controllers that do not process Modbus™ exceptions. The following exception codes are supported and
returned when Modbus™ exceptions are enabled:
Table 4
Exception Codes
Exception
Code
Name
Meaning
01 Illegal
Function
Unsupported function code. Only 03, 06 and 16 are
supported.
02
Illegal Data
Address
The registers being requested falls only partially within
the valid RXT-300 register ranges. For example, the
RXT-300 registers start at 8192. If an access is
perform requesting registers 8191 to 8192 then this is
an Illegal Data Address since 8191 does not fall
completely within the valid register range. This would
not be an exception though if register address 8190 to
8191 were used – this would be passed on to the
Modbus™ interface for a local device to respond.
There are other exception codes defined in Modbus™ but these are the only ones returned by the RXT-300.
5.3
Modbus™ Register Map & Description
When a HMI Panel or controller is attached to a RXT-300, all sensors can be read using their unique system
Modbus™ address. Additional control and status is available using various the Modbus™ address of the
RXT-300 itself. There are many registers that are reserved and if written to may cause the system to
malfunction. The following sections will describe each register or register set for the register maps.
NOTE:
A write to a Read Only register is allowed and returns a response but it does not
change the value of the register. In some devices this would return an exception code.
