Siemens 7SG164 Ohmega 400 Series Manual page 85

7SG164 Ohmega 400 Series Communications Interface
2 Connection Specification And Relay Settings
This section defines the connection medium as defined by IEC 870-5-103. Appendix A shows some typical
communication connections.
2.1 Recommended cable
200μm Plastic Coated Silica (PCS) or 62.5/125μm glass. All cables should be terminated with ST connectors.
2.2 Connection Method
Communication networks can be connected in star or optical ring format. The Optical Ring architecture requires
data to be passed from one relay to the next, therefore when using this method all relays in the ring must have
Data Echo = ON selected in the Communications Interface menu of the settings list. Otherwise this setting is to
be Data Echo = OFF. Appendix A illustrates a number of network arrangements.
2.3 Transmission Method
Half Duplex serial asynchronous transmission. In IEC 60870-5-103 the line idle state is defined as Light On.
This can alternatively be selected as Light Off in the Communications Interface menu of the settings list if
required for use with alternate hardware (See Section 2.5).
2.4 Transmission Rate
Rates of 115200, 57600, 38400, 19200, 9600, 4800, 2400, 1200, 600, 300, 150, 110 and 75 bits per second
(BPS) are provided. Only 19200 and 9600 BPS are defined in IEC 60870-5-103, the additional rates are
provided for local or modem communications.
2.5 Line Idle Setting
The line idle setting must be set to be either ON or OFF to be compatible with the device connected to the relay.
IEC 60870-5-103 defines a line idle state of Light On. Unless the device connected to it has a compatible fibre
optic port Sigma 4, a converter to connect it to a standard RS232C electrical interface is needed.
Alternately, it may be connected via a Sigma 3 Dual RS232 Port or Sigma 1 Passive Fibre Optic Hub.
The Sigma 3 Dual RS232 port provides a Fibre-Optic interface to a relay and 2 RS232 Ports. The RS232 system
port is typically connected to a control system. Both this and the Fibre Optic port would usually be hidden from
view inside a panel. The second RS232 port is local port. When it is in use the system port is automatically
disabled. The Dual port device has an internal link to define whether the fibre optic port will operate as Light On
or Off. Default is Off.
The Sigma 1 Passive Fibre Optic Hub provides fibre optic interfaces for up to 29 relays. It has a fibre optic port
to the control system and multi relay connect. Each of the 30 fibre optic ports can be configured for Light On or
Off operation. Default for all is Off.
2.6 Parity Setting
IEC 60870-5-103 defines the method of transmission as using Even Parity, however, in some instances an
alternative may be required, this option allows the setting of parity to None.
2.7 Address Setting
The remaining setting on the communications menu is the Address setting. The address of the relay must be set
to a value between 1 and 254 inclusive before communication can take place. Setting the address to zero
disables communications to the relay, although if it is in an optical ring it will still obey the Data Echo setting. All
relays in an optical ring must have a unique address. Address 255 is reserved as a global broadcast address.
2.8 Modems
The communications interface has been designed to allow data transfer via modems. However, IEC 60870-5-
103 defines the data transfer protocol as an 11 bit format of 1 start, 1 stop, 8 data and Even Parity which is a
mode most commercial modems do not support. High performance modems, for example, Sonix (now 3Com)
Volante and Multi Tech Systems MT series will support this mode, but are expensive. For this reason a parity
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