Industrial Modem MIU56 User Guide
MIU56Robert Way Page 10 2/28/2003
Operating Modes
Asynchronous Mode
Asynchronous Mode is the normal default mode of the modem. Control and monitoring is performed by executing
the AT commands using a PC fitted with suitable communications software.
Synchronous Operation
Your modem supports two synchronous modes. Mode 1 allows operation with computers which support
asynchronous and synchronous communication on a single RS-232 port. Mode 2 allows your modem to be
operated with dedicated synchronous terminals.
Although your modem can only operate over a single two-wire connection, it will still perform full-duplex
synchronous communication. Half-duplex operation could be simulated by controlling the state of the RTS and
CTS signals.
Terminal Speeds
Your synchronous terminal or host should use the clock signals provided by the modem to synchronise transmit
and receive data. The clock speed will represent the actual connection speed of the modem.
+ When synchronous mode is selected, your modem cannot operate in constant speed mode or use the error
correction or data compression facilities of the modem. Only variable speed mode is available in synchronous
connections (this refers to the modem's terminal speed).
Line Speeds
Your modem supports a number of synchronous line speeds.
When operating in synchronous mode, your modem should always be configured with a locked, non-auto-ranging
B setting (this refers to modem line speed).
For V.34, the B setting only sets the maximum speed. The modem will automatically determine the highest usable
speed for the line.
Synchronous Mode 1
Synchronous mode 1 is selected with the &M1 command.
• Type: AT&M1 <E>
Your modem will enter synchronous mode whenever it successfully connects to a remote modem.
You should also:
• Type: AT&D2 <E>
This allows hang up via your computerÕs DTR signal.
To return to asynchronous operation:
• Type: AT&M0 <E>
Synchronous Mode 2
Synchronous mode 2 is selected with the &M2 command.
• Type: AT&M2 <E>
Your modem will enter synchronous mode whenever it successfully connects to a remote modem.
You should also:
• Type: AT&D2 <E>
This allows you to dial and hang up.
When the terminal asserts the DTR signal (DTR makes an OFF-ON transition), your modem will dial stored phone
number zero. The phone number may contain dial modifiers.