Received Data Flow Control; Hardware Control (Rn); Software Control (&In) - US Robotics COURIER User Manual

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COURIER HIGH SPEED MODEMS
RECEIVED DATA FLOW CONTROL
Separate commands, &Rn (hardware) and &In (software), con-
trol the flow of Received Data passed by the Courier to your
DTE. Because most computers handle incoming data at a much
faster rate than the modem receives it over the phone line, you
may want to leave this type of flow control disabled.
Your software and machine must support whichever type you
select, although we recommend hardware flow control, if
possible. Review the quick-configuration guide that came with
the modem and, if necessary, your software and computer
manuals.
Hardware Control (&Rn)
When the DTE drops its Request to Send (RTS) signal, the
modem stops passing along received data. The DTE sends RTS
again when it is ready to receive.
Your DTE and software must support RTS. You cannot use this
type of flow control, however, if your software requires a
constant RTS signal.
WARNING: Use this type of flow control only for ARQ (error-
control) calls, because under error control the modems use flow
control across the phone link. During non-ARQ connections,
there is no way to signal the remote modem to stop sending
data. If your modem stops passing data to the DTE and the
remote modem keeps sending across the link, the Received Data
buffer will overflow.
&RO Delay Clear to Send Response after Request to Send signal
(RTS/CTS delay). The delay is required by some
synchronous mainframes and does not apply to
asynchronous calls. See Chapter 7.
&R1 The modem ignores RTS. Default. This setting is
required if your DTE or software does not support RTS.
&R2 Hardware flow control of received data enabled. The
modem sends data to the DTE only on receipt of the RTS
signal.
Software Control (&In)
When you send the modem a <Ctrl>-S (XOFF) command from
the keyboard, the modem stops passing received data to the
Interface Controls 4-9