3200 Series
Part No HA028651 Issue 7.0 Apr-09 79
15.2.1
Broadcast Communications
Broadcast communications as a simple master is available
on 3200 controllers from software versions 1.10 or
greater. Broadcast master communications allows the
3200 controller to send a single value to any number of
slave instruments. Modbus broadcast using function
code 6 (Write single value) must be used. This allows the
3200 to link with other products, without the need for a
supervisory PC, to create a small system solution.
Example applications include multi-zone setpoint
programming applications or cascade control using a
second controller. The facility provides a simple and
precise alternative to analogue retransmission.
The retransmitted parameter can be selected from
Setpoint, Process Variable, Output Demand or Error. The
controller will cease broadcast when it receives a valid
request from a Modbus master - this allows iTools to be
connected for commissioning purposes.
!
Warning
When using broadcast master communications, bear in
mind that updated values are sent many times a second.
Before using this facility, check that the instrument to
which you wish to send values can accept continuous
writes.
Note that in common with many third party
lower cost units, the Eurotherm 2200 series and the
3200 series prior to version V1.10 do not accept
continuous writes to the temperature setpoint.
Damage to the internal non-volatile memory could
result from the use of this function. If in any doubt,
contact the manufacturer of the device in question
for advice.
When using the 3200 series fitted with software version
1.10 and greater, use the Remote Setpoint variable at
Modbus address 26 if you need to write to a temperature
setpoint. This has no write restrictions and may also
have a local trim value applied. There is no restriction on
writing to the 2400 or 3500 series.
15.2.2
Broadcast Master Communications
The 3200 broadcast master can be connected to up to 31
slaves if no segment repeaters are used. If repeaters are
used to provide additional segments, 32 slaves are
permitted in each new segment. The master is
configured by setting the ‘RETRAN’ parameter to
W.SP
,
PV
,
OP
or
Err
.
Once the function has been enabled, the instrument will
send this value out over the communications link every
control cycle (250ms).
Notes:-
1.
The parameter being broadcast must be set to the
same decimal point resolution in both master and
slave instruments.
2.
If iTools, or any other Modbus master, is connected
to the port on which the broadcast master is
enabled, then the broadcast is temporarily inhibited.
It will restart approximately 30 seconds after iTools
is removed. This is to allow reconfiguration of the
instrument using iTools even when broadcast master
communications is operating.
15.2.3
Wiring Connections
The Digital Communications module for use as a master
or slave is fitted in Comms Module slot H and uses
terminals HA to HF.
☺
EIA232
Rx connections in the master are wired to Tx
connections of the slave
Tx connections in the master are wired to Rx
connections of the slave
☺
EIA485 2-wire
Connect A (+) in the master to A (+) of the slave
Connect B (-) in the master to B (-) of the slave
This is shown diagrammatically below
☺
EIA422 (4-wire) 3216 Only (option 6XX)
Rx connections in the master are wired to Tx
connections of the slave
Tx connections in the master are wired to Rx
connections of the slave
3200
Master
Slave 1
Slave 2
Slave
31
3200 Master
RS422
4-wire
Rx+
Rx-
Tx+
Tx-
Slave 1
RS422
4-wire
Rx+
Rx-
Tx+
Tx-
Com
Com
3200
Master
EIA232
Rx
Tx
Slave 1
EIA232
Rx
Tx
Com
Com
320
Master
S485
B (-)
A (+)
Slave 1
RS485
B (-)
A (+)
Com
Com