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CHAPTER 5: Command Mode
connected in Reliable mode, a different method of modem flow control
is used, and the commands for Normal Mode Modem Flow Control are
ignored.
When you are using Speed Conversion in Normal Mode, you must
activate the modem’s Normal Mode Modem Flow Control. (Speed
Conversion is explained in Section 5.4.11.)
Terminal/Computer Initiated Pacing &E13
As mentioned earlier, the Series II Modem can initiate flow control by
issuing Xon/Xoff commands or toggling the CTS signal on the RS232C
interface. The modem can also be configured to react to similar com-
mands and signals from the computer or terminal to which it is
attached via the RS232C interface. We refer to the computer or
terminal initiated flow control as Pacing. When the modem is set for
Pacing On, the modem will respond to the terminal or computer
pacing. When the modem is set for Pacing Off, it will ignore pacing.
In order for the Series II Modem to be set for Pacing On, a modem-
initiated method of flow control must be previously selected. Once this
is done, the Modem will respond to either Xon/Xoff commands, or to
the toggling of the RTS (Request to Send) signal on Pin 4 of the
RS232C interface, depending on what you selected earlier as your
Modem-Initiated Flow Control method.
Maximum Block Size &BS
The maximum size of Reliable mode data blocks can be controlled with
the &BS command. MNP 3 sends blocks of 1 to 64 characters. MNP 4
and 5 typically send blocks of 1 to 256 characters and LAP-M typically
send 128 characters. For MNP Classes 4 and 5 and for LAP-M, reducing
the block size to 64 characters may give a smoother flow of data, and
better throughput on noisy phone lines. Using smaller block sizes over
good phone lines may cause a slight loss in throughput (speed).
AT&BS0 = Maximum transmit block size of 64 characters
AT&BS1 = Maximum transmit block size of 128 characters
(LAP-M) or 256 characters (MNP)
The factory default setting is &BS1.