Operating Modes and Character Recognition
6NH7811-0AA22 © Siemens AG 2002 All Rights Reserved
4-2 MD2 Modem (07/2002)
Introduction
A variety of operating modes and character formats can be set on the MD2 modem
to optimally adapt the modem to the various requirements of the data terminal
equipment (DTE) to which it is to be connected.
Setting the operating mode is essentially the selection of the type of interface to be
used, the RS232 or RS485 port through which the modem connects to the DTE. In
addition to the operating mode, the transmission rate is usually set, which, like the
type of interface, is determined by the DTE.
The MD2 modem offers the basic baud rates 1200, 2400, 9600 and 19200 bps.
The MD2 uses a signal refresh logic to regenerate the received transmission signal
based on the baud rate set and thereby ensures error-free transmission of data.
The MD2 modem also features an operating mode for using baud rates less than
1200 bps. This operating mode, "Signal refresh off", turns of the signal refresh logic
permitting the modem to operate "transparently".
The various operating modes of the MD2 modem are described in detail in the
following section, 4.1 MD2 Operating Modes.
Setting the character recognition on the MD2 determines the type of asynchronous
data format to be used for transmission. The signal refresh logic also plays a role
here. This needs to be repeatedly re-synchronized during transmission of a data
block. The character recognition setting determines the point in time in which the
signal refresh logic is re-synchronized. This attribute enables operation of the MD2
modem at baud rates of 300 and 600 bps.
A detailed description of the character recognition and its properties is available in
section 4.2 Character Recognition of the MD2.
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