Flow Control; Protocol Commands - Motorola V.3400 User Manual

Note
In direct mode and the DCE link is established at a rate
other than the original DTE speed, the modem will issue the
connect message for the new DTE speed at the original
rate. All subsequent data will be sent to the DTE at the new
DCE speed.

FLOW CONTROL

If the serial port speed exceeds that of the modem connection, characters
may be sent by the DTE to the modem faster than it can send them to the
remote modem. The modem holds characters in an internal buffer until
they can be transmitted. When this buffer is full, the modem uses flow
control to cause the DTE to stop sending characters. As the modem
continues to transmit data and the buffer empties, flow control is again
used to cause the DTE to resume sending data. The modem can use
hardware flow control (RTS/CTS) or in-band flow control (XON/
XOFF).

PROTOCOL COMMANDS

These commands enable or control the various data compression, flow
control, and error correction options of the modem. Table 6-1 illustrates
mode and the associated features.
Table 6-1. Operating Modes and Conditions
Operating
Mode Correction
Normal Disabled
Direct Disabled
Reliable Enabled
(MNP and
LAPM)
Auto-reliable Enabled
(MNP and
LAPM)
Error Data
Compression
Not applicable
Not applicable
On or off
On or off
Flow
Control
Allowed
Not
applicable
Allowed
Allowed
V.3400
Protocols
Constant
Data Speed
Interface
Buffered On or off
Not DTE=DCE
buffered (slaved)
Buffered On
Buffered On
6-3