3Com U.S. Robotics 56K Voice, Command Reference Manual

Page: 93 / 210

Received Data Flow Control 11-3
Received Data Flow
Control
Flow control settings are controlled by the AT&Rn and AT&In commands.
The default settings are &R2&I0. Use the following table for more
information about setting the flow control.
For your modem to Command
Pause before sending CTS signal after receiving the
Request to Send (RTS).
AT&R0
Ignore the RTS signal.
&R1 is required if your computer or software does not
support RTS
AT&R1
Enable hardware flow control.
The Business Modem sends data to your computer only
upon receipt of the RTS signal.
AT&R2
Disable software (XON/XOFF) flow control.
Recommended for non-ARQ (Normal mode) calls (see
AT&I5). While the Business Modem
is online, the only
characters it recognizes are +++, the escape code.
AT&I0
(Default)
Enable software (XON/XOFF) flow control. Use in ARQ
mode only.
Keep in mind that the XON/XOFF characters sent to the
remote computer may interfere with XON/XOFF signaling
between the remote computer and remote device (see
AT&I2).
AT&I1
Force the Business Modem to act on your XON/XOFF
commands, but remove them from the data stream
instead of passing them to the remote computer.
This ensures that the remote computer does not confuse
your XON/XOFF characters with those from its attached
device. This is the recommended setting for ARQ mode.
AT&I2
When using the AT&I2 command, if the call is not in ARQ mode, there is no flow
control on the link. If you send an XOFF to your modem and it stops passing data,
it has no way to tell the remote computer and modem to stop sending for a
while, and the local’s buffer may overflow. For more reliable control in non ARQ
mode, see AT&I5.
Enable Hewlett Packard-Host mode. Applies only to
devices attached to an HP mainframe that uses the
ENQ/ACK protocol. Use in ARQ mode only.
If you want to use software flow control to transfer
non-text (binary) files, set serial port and connection rates
equal using &B0 and & N0. See Chapter 9,
Controlling
Data Rates for more information about these commands.
AT&I3