2.3 Station address

The station address is set using both coding switches. The settable address is within the 01 and 99 range. The value 00 is reserved for the programming and configuration mode.

The lower coding switch serves for setting the address tens digit, the upper coding switch for setting the units digit. The address is only read in and saved when switching on. Changes made during operation have no effect.

The following example shows the setting of address 62:

Fig. 2.5: Coding switch

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2.4 Mode switch

Fig. 2.6: Mode switch

The mode switch is only available in the controller and permits a manual Run/Stop- status change.

ATTENTION!

If when changing over the mode switch from ‘Run’ to ‘Stop’ outputs are still activated, these will remain in this status! Switching off on the software side, e.g. by initiators is then ineffective because the program will no longer be processed!

(A mode change over is made internally at the end of a program cycle‘.)

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2.5 Fieldbus connection

2.5.1 RS 485

Coupler : 750-312 and 750-315

Controller: 750-812 and 750-815

One transmission medium for the MODBUS is RS485, whereby, 2 or 4 wire can be used. The following figure shows an example for a 2 wire version:

Fig. 2.7: 2 wire connection

As opposed to the above the 4 wire connection offers the advantage that it can use simpler repeaters and converter. The following illustration is a corresponding example:

Fig. 2.8: 4 wire connection

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Connect the D-SUB connection plug as follows:

Table 2.2: Pin assignment for 4 wire connections

The connection point is mechanically lowered so that fitting into a 80 mm deep switch cabinet is possible following the plug-in connection.

The pin assignment is 2 wire operation conforms with the Profibus assignment. Thus the Profibus wiring components can be used.

One application possibility is the connection of a Yokogawa Interface. This PCB supports the MODBUS protocol. The standard setting is the RTU mode (see chapter MODBUS) and 4 wire connections. The pin assignment is as follows:

Table 2.3: Yokogawa interface pin assignment

Switches for RS 485

The setting for 2 or 4 wire connections and switching in or out of the corresponding matching resistors is made by switches, covered by the enclosure. To access the switches remove the enclosure from the coupler/controller. A protruding locking device can be found on the bottom of the unit on the two short sides. Push the two short sides apart to permit the enclosure to be pushed past the unit metal plate. Simultaneously press from above on the right hand section of the coupler/controller, which is the supply side.

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The enclosure prevents unintentional changes of the settings during later operation. If, however, access to the settings is required in the case of a fault, ensure that the previous settings are marked on a label.

After changing the settings push the enclosure back onto the coupler/controller. Note that it may be necessary to lightly push the wide side of the coupler/controllers to the side when the metal plate does not easily slide into the enclosure. In addition it may be necessary to push the rotary switches into the cut-outs provided.

The switch on the interface printed circuit board for setting 2 and 4 wire connections or for the matching resistors can be found in the following illustration:

Fig. 2.9: Interface printed circuit board

For 2 wire connections RxD and TxD are short circuited. By the termination, a series circuit comprising of 3 resistors is connected to the bus conductor terminations.

Fig. 2.10: Internal matching resistors and interface switches

The standard setting for the supplied coupler/controller is a 2 wire connection and a switched off matching resistor.

Four wire connections can be terminated as well as the receiver line.

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2.5.2 RS 232

Coupler : 750-314 and 750-316

Controller: 750-814 and 750-816

The MODBUS can also be operated directly on an RS 232 interface. The D-SUB connection plug is connected in this case as follows:

Table 2.4: RS 232 plug assignment

The pin assignment permits the use of commercially available 9 pole 1:1 sockets/ plug lines for direct connection to a PC.

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