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DIVA T/A ISDN Modem Reference Guide
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Page 42
V.120 Configuration Commands
The following AT commands pertain to V.120 configuration on your DIVA T/A.
AT!E0=n
V.120 N201 Tx (Maximum Transmit Frame Size)
. N201 Tx (Maximum Transmit Frame
Size) determines the maximum number of octets in an information field to be
transmitted to the remote V.120 device.
Range: 16 to 260.
Default: 260.
Note: If a larger frame needs to be transmitted, the DIVAT/A segments it into V.120
fragments and expects the remote device to perform reassembly.
AT!E1=n
V.120 N201 Rx (Maximum Receive Frame Size)
. N201 Rx (Maximum Receive Frame
Size) determines the maximum number of octets in an information field to be received
from the remote V.120 device.
Range: 16 to 260.
Default: 260.
AT!E2=n
V.120 Multiframe Mode
. The V.120 protocol supports two different transfer modes
described below:
n=E Multiframe mode is enabled (default). This mode provides acknowledged
transfers by using Information (I) and acknowledgment (RR/RNR) frames, and
provides error correction and recovery procedures. The link verification
procedure is provided by exchanging SABME and UA frames.
n=D Unacknowledged mode is enabled. This mode uses Unnumbered Information
(UI) frames. The link verification procedure is provided by exchanging XID frames.
The unacknowledged mode is less robust than multiframe mode.
Note: The DIVA T/A may automatically switch to the other mode if the link verification
frames issued from the remote device do not match the configured mode on the local
device. The DIVA T/A always prefers the multiframe mode.
AT!E3=n
V.120 K Window Size
. Applicable to the multiframe mode only. K (Window Size)
determines the maximum number of sequential data frames that may be outstanding
(not acknowledged) at any given time.
Range: 1 to 127 frames.
Default: 7.
AT!E4=n
V.120 T200 (Retransmission Timer)
. Applicable to the multiframe mode only. T200
(Retransmission Timer) is the maximum time allowed to determine if a transmitted
frame was received by the remote device, prior to its retransmission. The unit of
measurement is 1/10 of a second.
Range: 1 to 255.
Default: 15 (equal to 1.5 seconds).
The value specified for T200 (Retransmission Timer) must be less than the value
specified for T203 (Link Integrity Timer) (see “AT!E6=n” on page 43
). Otherwise, the
default values are used.