216 • SMP Gateway User Manual
23.1 Specifying which serial ports have modems
To indicate that a modem is connected to a specific serial port:
Start SMP Config from the SMP Manager window.
In the left pane, click Serial Ports.
In the right pane, in the Interface drop-down list of the corresponding serial port, click
Modem Asynchronous.
23.2 Creating a modem pool
A modem pool manages a certain number of physical modems so that when an outgoing call is to
be made, the pool selects an available modem to perform the call. Similarly, when an incoming
call is received, the pool identifies the caller and dispatches the call to the appropriate connection
(eventually to the protocol component).
There must be at least one modem per pool. In the case of the SMP 8-40, all the modems in a pool
must be connected to serial ports on the same board.
When it receives an incoming call, a modem pool needs to identify the caller in order to dispatch
the call to the appropriate protocol component. Since the identification is protocol-specific, each
protocol has its own method for identifying the caller. The identification procedure returns the
caller’s DEVICE ADDRESS. This DEVICE ADDRESS is then compared with the DEVICE
ADDRESS of each modem pool slave connection connected to the pool. Note that a modem pool
slave connection DEVICE ADDRESS is set by the protocol components. When a match is found,
the communication path is set up from the modem pool slave connection to the modem.
Identification is performed by the Call Dispatcher. The identification procedure for each protocol
supported is specified in the table next.
Protocol Identification Procedure
IEC 60870-5-101 The Call Dispatcher sends an IEC 60870-5-101 RESET OF LINK
broadcast frame. The slave device is expected to respond with an ACK
frame containing its own DEVICE ADDRESS.
DNP3 The Call Dispatcher sends a DNP3 RESET OF LINK broadcast frame.
The slave device is expected to respond with an ACK frame containing
its own DEVICE ADDRESS as the source address.
To add a modem pool:
In the left pane, click Serial Ports, then on Modem Pools.
In the right pane, type the name of the pool.
Edit the modem pool settings.
These settings set up the behavior of the Call Dispatcher, as described in the table next.
To Next Page
Loading...