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Appendix C Hayes AT Command Reference

RFI-9256 Radio Modem User Manual Page 78 of 96

C.1.11 “AT&D” Data Terminal Ready Activity

Data Terminal Ready (DTR) is an RS-232 signal used to indicate to the radio whether the DTE is ready to

communicate. The

AT&D

command is used to tell the radio how it will react when the DTR signal changes.

The options are shown in Table 28.

Command Description

AT&D0

The radio ignores the DTR signal.

AT&D1

The radio enters local command mode whenever DTR is low.

AT&D2

The radio hangs up the current connection whenever DTR goes from high to low.

AT&D3

The radio hangs up and returns to the local command mode whenever DTR is low. The radio

with this configuration must be DTR asserted before dialling or answering otherwise an

immediate hang-up will occur.

Table 28: AT&D data terminal ready activity commands

C.1.12 “AT&F” Restore Factory Defaults

All configuration values in the RFI-9256 have factory default settings, outlined in Appendix D. The

AT&F

command can be used to reset some or all of these settings to the factory default state.

Command Description

AT&F0

Restores the Hayes radio interface to the factory default settings.

AT&F1

Restores all radio settings to their factory default state.

Table 29: AT&F restore factory defaults commands

C.1.13 “AT&G” Exclusive Port Control

There are times when a DTE may require exclusive control of a radio. Since the RFI-9256 is a dual port

radio, this involves preventing any dial attempts from the other serial port. There are three options for

exclusive port control

Command Description

AT&G0

Multi-port operation.

AT&G1

Exclusive port control. The other serial port will always return

BUSY

whenever an attempt is

made to dial out.

AT&G2

Priority port control. If the other serial port already has a connection established then it will

be immediately disconnected when the priority port (this port) issues a dial command, and

the other serial port will always return

BUSY

whenever an attempt is made to dial out.

Table 30: AT&G exclusive port control commands