ATCommands

V.25bis Operations

V.25bis is a modem command set like the AT command set, which allows you to control your modem. However, V.25bis commands may be issued to the modem in asynchronous or synchronous mode (AT commands may only be issued when the modem is operating in asynchronous mode). This means V.25bis is suitable for mainframe and minicomputers which only support synchronous communications ports. The implementation of V.25bis supported by your modem is based upon the 1988 revision of the V.25bis specification, however not all aspects of the V.25bis specification have been implemented.

V.25bis operation is supported in both smart and dumb modes.

Selecting V.25bis Operation

To select V.25bis mode, issue the appropriate #M command. Three V.25bis modes are supported by your modem:

oAsynchronous V.25bis. The modem operates in asynchronous mode using V.25bis command rather than AT commands. Issue the AT#M1 command to select this mode.

oSynchronous V.25bis with HDLC framing. The modem communicates and accepts V.25bis commands in synchronous mode with HDLC framing. Issue the AT#M2 command to select this mode.

oSynchronous V.25bis/BSC mode. The modem communicates and accepts V.25bis commands in synchronous mode with character framing (BSC mode). Issue the AT#M3 command to select this mode.

The &W and Z commands must be issued after the #M command in order for V.25bis command mode to be selected. Alternately, issue the &W command after the #M command and switch the modem off and on or lower DTR (after an &D3 command has been issued).

When you reset the modem (for example, you issue the &F command or issue the RST command or switch the modem off and on), you must issue an ATZ command to select V.25bis command mode; your modem always resets and powers-up in AT command mode, regardless of the setting of the #M command.

If your modem has Option switches to select V.25bis operation, the setting of the Option switches always take precedence over the #M command.

The %R2 option will be required for most V.25bis setups. This setting ensures that the CTS signal is only asserted when the modem is ready to accept a new command (in command mode).

Page 63

Page 63
Image 63
Telenetics 56 manual 25bis Operations, Selecting V.25bis Operation