Code: MSGB202$0500.doc 18/06/2004 P. 19 / 20
APPENDIX A – Connection modes
Connection via standard modem
To make a remote connection via a switched telephone line the use of a pair of modems is necessary.
Lovato Electric guarantees correct operation of the connection using modems of the following type:
•
3-Com U.S. Robotics 56K model 5630
Though correct operation is possible also with modems of other types, in this manual all the configuration
commands (variables depending on the manufacturer) and the connection diagrams will refer to the above-
mentioned modem model.
Though very simple in conception, connection via modem requires that the installer have a minimum
of experience concerning the problems connected with serial communication, modem programming,
types of telephone lines, etc. In an attempt to simplify the configuration procedure as far as possible,
we have subdivided the operations to be carried out in the following steps:
1. Modem configuration at the DMK end
From the DMK end the modem must be configured before it can be used. Configuration serves to
implement the following functions:
•
Disable the echo
•
Set a communication speed (this must be the default speed for DMK also)
•
Permanently store the two previous settings as default at switch on
To make these configurations, the modem to be connected to the RS232/RS485 converter will have to
be momentarily connected to the PC with its standard cable. Then start the PM.EXE program (supplied
together with this software) and press the
Program modem
button
.
Wait for the confirmation message
and then disconnect the modem from the PC and connect it to the DMK. The PM.EXE program transmits
the following configuration string to the modem:
AT E0 &N6 &U6 &W0
<CR>
(commands valid for modem model 5630)
To select higher baud rates in the modem, digit Nx & Ux, whereas x is the rate code to be obtained.
Take into account the rate to select is the one at the multimeter end.
If the program PM is used, the AT&Nx and AT&Ux string must be changed in the modem.txt file found in
the same directory where the PM program is installed.
If the user is familiar with terminal emulation programs (such as Windows Hyperterminal) this
programming can be done manually without the aid of the PM.EXE program. In this case, it will be
necessary to set the serial interface at 9600 Baud, 8 bit, No parity, 1 stop bit and type in the above string
from the keyboard. On pressing return the modem will answer with OK confirming that programming has
taken place.
2. DMK
configuration
Also the DMK needs a configuration to be able to converse with the modem.
•
From the front panel of each DMK, enter the serial communication setup menu (see the DMK Addendum
Manual)
•
Check the serial address (parameter P.41). If several DMKs are connected to a RS-485 bus, set each of
them with a progressive serial address starting from 001.
•
On each unit, select the Modbus ASCII protocol (parameter P.44 set to ASC).
•
If you want the DMK to answer when modem rings (modem without auto-answer) then set parameter
P.45 to 001, only for the DMK with serial address 01.
•
Otherwise, if you want the modem to answer automatically itself, then enable the modem auto-answer,
setting its parameter S0 to 001 (with command ATS0=1 &W0) and leave the first DMK with P45 to 000.