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3.5 Dial On Demand
The dial on demand facility enables an FX or AnS PLC to command the modem to
dial pre-stored telephone numbers and automatically exchange data with a remote site.
IMPORTANT NOTE:
The facilities described in sections 3.5 and 3.6 will not operate from an An(S)/QAn(S)
PLC when connected via an HMI.
The pre-stored telephone numbers may be either speed dial numbers (stored in the
modem) or located within PLC registers. How to set up the telephone numbers is
explained in section 3.5.5.
The data exchanged may be to either send fixed text messages stored within the
modem or to read/write blocks of data from within the PLC. The process of setting up
fixed text messages is explained in section 3.5.6, while data transfers are dealt with in
section 3.6. Alternatively the modem can be commanded to stay on line either to
repeat the data transaction, or wait on line until instructed to hang up by either end.
Dial on demand operates by configuring the modem to poll a block of PLC
(command) registers, which provide the modem with instructions, explained in
section 3.5.3.
NOTE: Throughout this section the
Local
system is the one making the call, while the
Remote
system is the one being called.
3.5.1 Setting Dial on Demand Commands
To set up Dial On Demand it will be necessary to connect a PC directly to the modem
via the PC serial port and the RS232 data connector. Use the MODEM-PC9-CAB or
suitable lead and run your terminal software.
1) Defining the local PLC type
Because different PLC’s use different communications protocols it is necessary to set
the modem to the type of PLC that it is connected. This is done by entering a protocol
code with the command:
AT%ADP =
x
Where x =0
No protocol/Desk (factory default version 1.20 or later)
All other protocols are listed in section 5.9.
