KE LOGEM LGH 28.8D1, Operation Manual, Page: 189 / 200

189 Operation Manual V.34 - Modems, Version 07/97
Chapter 8
normal mode The modem buffers data coming from the DTE. For
this reason the transmission rate DTE/modem may
differ from the modem to modem transmission rate.
To prevent data losses the data flow control has to
be activated. The modem processor controls the
data transfer from the modem buffer. During normal
mode data transmission is performed without data
protection protocols.
reliable mode Corresponds to normal mode. As an addition data
protection protocols (MNP4, V.42) are active. The
establisment of a connection is terminated if the
modem operates in reliable mode and the remote
modem does not support any data protection
protocols.
autoreliable mode Data transmission is possible with or without data
protection.
speed buffering Speed buffering guarantees for constant interface
rates towards the terminal equipment if multimode
modems are employed that support different
modulations.
data flow control Data flow control is implemented to avoid data loss
during transmisson. Data loss may occur whenever
the data buffer of the modem overflows. The modem
has to prevent in such cases the terminal equipment
from transmitting further data. Data flow control is
possible as:
a)
hardware flow control; the signals S2 and M2
(RTS and CTS) of the V.24 interface are em-
ployed for flow control.
b) software flow control; the XON and XOFF
characters are employed for flow control;
the connection is not transparent.
data protection The data protection protocol is employed to correct
protocol transmission errors. The modems come with imple-
mented protection protocols. For this reason the
terminal equipment transmits and receives only
effective data. At an active data protection protocol
transmit data is formed to blocks and transmitted
with a checksum. The receive side computes the
Appendix