Operating Modes and Character Recognition
6NH7811-0AA22 © Siemens AG 2002 All Rights Reserved
4-26 MD2 Modem (07/2002)
4.2.4 "MID off" Character Recognition
Similar to "MID on" character recognition "MID off" character recognition is
designed to transmit data streams consisting of any format. This type of character
recognition is especially suited to transmit data streams which are available from
the DTE at less than the baud rate set on the modem. The baud rate set on the
modem must be an even multiple of the baud rate set on the DTE. The DTE can
therefore be operated at baud rates 600, 300, 150, 75, etc..
Message interval detection is switched off if "MID off" character recognition is
selected. However, in order for the receiving modem to still be able to detect the
end of a message, the sending modem needs to switch off its transmitter after the
final character of a message. This is accomplished by withdrawing the RTS signal
on the sending modem. The following illustration shows this mechanism from the
viewpoint of the sending modem.
Fig. 4-24 RTS and TxD signals
The method described above means that "MID off" character recognition can only
be used in combination with the "Normal" operating mode.
Another characteristic of "MID off" character recognition is that the idle state of the
data signal on the WAN line can be set to either "0" or "1". However, this property
has no effect on the data transmission.
The following table summarizes the various characteristics of the "MID off"
character recognition.
Table 4-5 Summary of the characteristics of "MID off" character recognition
Character recognition Settings on the 10-pin
DIL switch
Length of
message
interval
Idle state of
the data
signal
Possible
baud rates
(in baud)
MID off
idle state 0
0
MID off
idle state 1
unlimited
1
...., 75, 150,
300, 600,
1200, 2400,
4800, 9600,
19200
RTS
TXD
1234
OFF
ON
5678910
1234
OFF
ON
5
6789
10
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