Westermo RM-455U-D - Manual (Page 40)

Chapter Three Configuration
Man_455U-D Rev 3.04 Page 41
 “XON / XOFF” the modem uses the XON and XOFF symbols to control flow of data.
This protocol should not be used with raw binary data, as the raw data may contain the
XON and XOFF characters. This flow control method is only suitable for use with ASCII
data.
3.6.3 Other Settings
Select the “Modem” tab:
CRC Error Checking for transmitted messages
It is normal for error checking to be disabled for Unacknowledged mode and enabled for
Acknowledged. However you can select either for either mode, and separately select for the
RS-232 port and the RS485 port. The modem is always able to receive messages both with
and without error checking, so different modems in the system may be configured with
different error checking options.
Security Encryption
Data Encryption may be set to:
 “Disabled” setting allows the modem to receive both encrypted and unencrypted
messages, but the modem will only transmit unencrypted messages.
 “Enabled on TX” causes the modem to transmit encrypted messages and to receive both
encrypted and unencrypted messages.
 “Forced on RX” causes the modem to transmit encrypted messages and only accept
messages which are encrypted.
Note that the encryption keys must be set up in each modem to the same values to allow the
modem to decrypt encrypted data correctly. If incorrect encryption keys are entered, the data
will be forwarded out the correct port, but will not be correctly decrypted at the receiver. To
set the security key, connect to the modem locally and use the configuration software, or using
AT commands, enter the command AT#S. Note that the security key can not be changed
remotely.
DTR Control
The DTR signal on the RS232 port can be used for different functions.
 “Ignore DTR” - the DTR signal does not perform any function
 “Command Mode” - if the host resets DTR, the 455U-D will go into command mode -
when DTR is activated, the module will revert to on-line mode
 “Command Mode, Disconnect” - as above except that the module will also force a
disconnection of the communications link
 “Low Power, Disconnect” - when the host resets DTR, the module will disconnect the link
and go to low power mode. If you select the “Low Power” option in the Acknowledged
mode page, this selection of DTR will be automatically made - refer to the “Low Power
Mode” section of this manual.