© Danfoss A/S (AC-MCI / sw), 2014-11
DKRCC.PS.RQ0.B7.02 /520H8832
7
Manual
Superheat Controller EIM 336
MODBUS Communication
Setting up modbus parameters
The modbus baud rate, “Modbus Baud”, can be set to three
different baud rates. The modbus parity “ModbusParity” can be set
to either no parity, odd parity or even parity. The modbus stop bit
can be set to either 1 or 2 stop bits. The default settings are 19200
baud, even parity and 1 stop bit.
A jumper KM7 has been added to the EIM 336, for selecting
between two predefined addresses. This is useful for applications
such as reversible air conditioning/heat pump systems with both
an indoor and an outdoor unit. In this way the address can be
changed without the need to reconfigure the controllers settings.
The primary unit address “o03 Unit addr.” is used when the jumper
is mounted. The secondary unit address “Unit Addr. 2” is used
when the jumper is not mounted. The default primary address is
165, the default secondary address is 164.
Note:
Changes to these parameters will become active immediately.
This means that a modbus tool or controller that changes these
settings will loose connection to the EIM 336 and will need to
reestablish connection using the new settings.
The EIM 336 “read holding registers” function (0x03) is limited
to a maximum of 20 consecutive registers per read request. If
a modbus tool or a controller is used to read parameters over
modbus, it needs to take this into account.
During the communication the transmitted Modbus requests are
checked for CRC errrors. If the CRC is not correct, the request is
discarded and the EIM 336 waits for a new request. In this case no
exception response is issued.
Related parameters:
Symbolic name
PNU
Description
o03 Unit addr.
2008
Primary unit address is used when jumper KM7 is mounted
--- Unit Addr. 2
2009
Secondary unit address is used when the jumper KM7 is not mounted
--- Modbus Baud
50060 Communication setting baud rate, 0 =9600 , 1 = 19200, 2 = 38400
--- ModbusParity
50061 Communication setting parity, 0 = no parity, 1 = odd parity, 2 = even
--- ModbusStopB
50062 Communication setting stop bit, 1 = 1 stop bit, 2 = 2 stop bit