Elpro Technologies 905U-D User Manual download pdf (Page 40)

905U-D Radio Modem User Manual

Man_905D_1.10.doc Page 40

 “Always On” - the 905U-D sets the DCD to be always on

 “Only High When Connected” - the DCD signal will be on when the link is connected and

off when the link is reset

 “Pulse Low on Disconnect” - the DCD signal will be normally on but will switch off

momentarily (for 0.1 sec) when the link is reset.

Advanced Settings

These settings may be adjusted if the host device is using AT commands - refer to Appendix A

for an explanation of the different parameters.

S Registers

These are parameter registers settable by AT commands. They do not normally need to be

changed. Refer to Appendix A for an explanation of these parameters.

4.5 Hayes Commands

The 905U-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 905U-D unit will accept Hayes commands, it must be in “command” mode. 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 905U-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 controlled mode.

Once in configuration mode, the 905U-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 115200 baud. B selects the radio

rate parameter and 2 is the value corresponding to 115200 baud.

Summary

Enter command mode <1sec break> + + + <1 sec break>

Response from 905U-D OK

Enter configuration commands ATxy

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Elpro Technologies 905U-D User Manual Page 40