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5 Serial protocol types
5.1 Modbus slave
If the paperless recorder is configured as a slave,
see Chapter 3.4 Configuration of the serial interfaces, Page 12,
in the network it responds to Modbus requests of the master.
The master controls the data exchange, the slaves only have a response
function. They are identified by their device address.
The master usually is a PC with a setup or visualization program installed. The
master can inquire all instrument variables of the paperless recorder (see
Chapter 7 Address tables, Page 47).
Modem
operation
• A paperless recorder in the slave mode can be controlled by the master via
a telephone connection using a modem, see above illustration.
• The paperless recorder can initialize a modem (also cyclically, if the modem
is switched on after the instrument has been activated).
• The paperless recorder can use the Init string (entry per setup program in
the "RS232/RS485: Modem" mask) to configure the modem so that an
incoming call is automatically answered. Then a remote inquiry for the
paperless recorder can be carried out by the master using Modbus
commands or the recorder can send a signal (e.g. an alarm) or an email
after the active dial-in.
• The paperless recorder (slave) can use a dial-in/hang-up string to alarm a
PC (master) with the suitable Modbus master software (which recognizes
incoming modem calls).
• The paperless recorder can use a dial-in/hang-up string to call an internet
provider and send an email.
When the modem operation is active, the following parameters (by setup
program only) can be edited:
In a Modbus network, only one instrument may be assigned with
the master function.
Modem
PC
(Master)
ModemModem
PC
(Master)
Telephone
Modbus
Slave Slave Slave
Slave
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