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5.9
Pacing ( &E13 )
As mentioned earlier, the MT2834MR6 can initiate flow control by issuing XON/XOFF commands or by
toggling the CTS signal on the RS-232 interface. The modem can also be configured to react to similar
commands and signals from the computer or terminal to which it is connected by the RS-232 interface.
Pacing is computer-initiated flow control. When pacing is enabled on the modem, the modem responds to the
terminal or computer pacing. When pacing is disabled on the modem, the modem ignores pacing.
Before you enable pacing on the MT2834MR6, you must select a flow control method. When pacing is
enabled, the MT2834MR6 responds either to XON/XOFF commands, or to the toggling of the RTS (Request
to Send) signal on Pin 4 of the RS-232 interface, depending on what you selected as your flow control
method.
5.9.1 XON/XOFF Pass-Through ( &E7 )
So far, you have had three choices to make regarding pacing. You can set the modem to respond to XON/
XOFF pacing, or to respond to RTS pacing, or you can set the modem to ignore pacing completely.
Another choice you can make (which actually can apply to both pacing and flow control, although it applies
mainly to pacing) is XON/XOFF pass-through. If your modem is set to respond to XON/XOFF commands, you
can have the modem do one of the following.
a.
The modem responds to the XON and XOFF pacing commands while at the same time allowing
these commands to pass through the modem and on to the remote location. We call this
"respond, pass-through."
b.
The modem responds to XON/XOFF pacing, but does not allow the pacing signals to pass
through the modem and on to the remote location. We call this "respond, no pass-through."
When XON and XOFF commands are allowed to pass through the modem, the computer at the remote site
receives these commands, and depending on how it is configured, the computer may respond to them also.
5.9.2 Non-Error Correction Mode Flow Control ( &E10 and &E11 )
You can use XON/XOFF to control the flow of data between two MT2834MR6s that are connected in non-
error correction mode. Disable or enable this method of flow control by using the Non-Error Correction Mode
Flow Control commands. When the modems are connected in reliable mode, a different method of modem
flow control is used, and the commands for non-error correction mode flow control are ignored.
You must enable non-error correction mode flow control if you use speed conversion in non-error correction
mode.
5.9.3 Hewlett Packard ENQ/ACK Pacing ( &E9 )
If the MT2834MR6 is used with Hewlett Packard or similar equipment that employs ENQ/ACK pacing, you
can configure it to respond to the ENQ/ACK commands used by Hewlett Packard systems. Doing so does not
effect any other flow control or pacing already configured in the modem.
When the MT2834MR6 is configured for ENQ/ACK, the ENQ (Ctrl-E) and ACK (Ctrl-F) signals from the HP
equipment will be accepted and responded to according to the Hewlett Packard protocol.
Chapter 5 - Error Correction, Data Compression, and Speed Conversion
73
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