User's Manual

38
Modem 34336
The Buffer Mode/Speed Conversion option Hayes, V.25 bis, Dumb, Leased
line modes (except V.33). It enables or disables speed conversion (for
asynchronous operation only) between the DTE and modem when error
correction is not used.
• ENABLE — When error correction is not enabled, the V.42 circuit
functions as a buffer between the DTE and the modem and provides
transmission speed conversion.
• DISABLE — Speed conversion is not allowed.
The DTE Speed option is available for Hayes, V.25 bis, Dumb, Leased-Line
modes (except V.33). It controls the DTE speed; however, it is effective only
when the modem is operating in V.42 mode, MNP mode, or buffer mode.
The DTE speed can be set for 115,200, 57,600, 38,400, 19,200, 9600, 4800,
2400, 1200, 600, 300, or 110 bps. The default "DTE speed" is 38,400 bps.
DTE speed refers to the speed of data transfer between the DTE and the local
modem. It is not necessarily the same as the data transmission speed between
the connected modems. If flow control is disabled, the DTE speed must be
equal to or less than the modem speed, and the local and remote DTE speeds
must be equal.
For Hayes mode operation, the DTE Speed option sets the default DTE speed
that will be effective after powerup or after a full modem reset. However, the
default DTE speed is automatically overridden when the Modem is
autobauded (when an AT attention code is sent to the Modem).
The Flow Control options control the data flow according to the availability
of memory space in the V.42 buffer. Flow control can be set independently
for the modem to the terminal and for the terminal to the modem. The
flow-control options include DTE-DCE, DCE-DTE and Pass-Through Flow
Control, and Flyback Buffer.
NOTE
When flow control is disabled, the DTE data rate must be equal to or less
than the modem data rate, and the local and remote DTE data rates must
be equal. (This precludes the need for flow control, which some
computers and terminals cannot handle, and avoids buffer overflow.)