User's Manual

Chapter Three Configuration
Man_455U-D Rev 3.01 Page 49
DNP3
The end of the DNP protocol frame is indicated by a period of no data transmission equal to
the configured timeout for that serial port (Configured in S19 for the RS232 port and in S21
for the RS485 port).
3.11 Advanced Settings - S Registers
These are parameter registers settable by AT commands or the Configuration software to fine-
tune the operation of the 455U. In most applications they do not need to be changed. Refer to
Appendix C for an explanation of these parameters.
3.12 Hayes AT Commands
The 455U-D unit may be configured by a host device using Hayes AT commands.
Configuration may be done “off-line” by a user (with a PC terminal as the host device) or it
can be done automatically “on-line” by a host device such as PLC or SCADA. The AT
commands are ASCII messages designed for use with conventional telephone modems.
Before a 455U-D unit will accept Hayes commands, it must be in “command” mode. The RJ-
45 configuration port is always in command mode. The DB9 RS-232 port needs to be set to
command mode if the modem is currently communicating. A host device may force the unit to
command mode by sending a sequence of three “escape” characters - “+++”. The default
escape character is “+”, however this may be changed as it is one of the configuration
parameters. There must be a 1 second break of data before and after the escape sequence. The
455U-D can be configured to start up in command mode (or alternately in operating mode). It
would be normal for the modem to start up in command mode when used in single-connect
Acknowledged mode.
Once in configuration mode, the 455U-D unit will accept a string of Hayes commands, and the
configuration changes made. The changes will not however be stored in permanent memory
(EEPROM) unless the Hayes command for recording the configuration (AT&W) is sent.
When the configuration changes are made, the module must be put back into its operating
mode by using the “online” Hayes command, ATO
Commands are entered in the format ATxy, where x selects the parameter, and y the value of
the parameter. For example, ATB2 sets the radio data rate to 4800 baud. B selects the radio
rate parameter and 2 is the value corresponding to 4800 baud.
Summary
Enter command mode <1sec break> + + + <1 sec break>
Response from 455U-D OK
Enter configuration commands ATxy