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D-Channel X.25
Parameter 5: Ancillary Device Control
Value
0
No PAD flow control
1
PAD data transfer flow control
2
PAD data transfer and PAD command mode flow control *
*default
Parameter 6: Control of PAD Service Signals
12-22
Parameter 5 specifies whether or not flow control of the local
DTE device (ancillary device) by the PAD can occur, and if so,
what modes of the PAD the PAD flow control of the local DTE
are allowed. Flow control of the local DTE device is handled in
conjunction with S54 (DTE flow control register). The type of
flow control the PAD transmits to the local DTE device is set
according to the setting of S54. For example, if S54 is set for
CTS flow control, the PAD will flow control the local DTE
device by turning off the CTS pin when the PAD can no longer
accept any characters from the local DTE. When the PAD can
resume accepting characters from the local DTE, the PAD turns
the CTS pin on. If all the DTE flow control options are disabled
(default), the PAD will transmit XON (Ctrl Q) and XOFF
(Ctrl S) to the local DTE for flow control.
Table 12-11: Ancillary Device Control
Description
Note: The function of parameter 5 differs from the 1984 CCITT
X.3 Specification. The specification indicates that only XON
and XOFF can be transmitted to the DTE for the purpose of
flow control. The TA does not restrict the type of flow control
used on the local DTE. The setting of the AT command indicates
the type of flow control sent to the DTE. Thus, if the DTE device
only recognizes CTS flow control, the PAD can still flow control
the DTE.
Parameter 6 specifies whether the PAD prompt or PAD service
signals are transmitted to the local DTE device by the PAD, and
the format of those service signals. The PAD service signals are
character messages transmitted to the local DTE device by the
PAD in response to PAD commands issued by the local DTE
or to inform the user of a packet or network action (i.e., call reset
etc.). The PAD prompt is the character *. It is transmitted by
the PAD to the local DTE device when the PAD is in PAD
command mode to prompt the user to enter a PAD command.
For non-interactive applications, the service signal transmission
to the local DTE may be disabled as the transmission service
signals can appear to be part of the received data.
UTA220/UTA220k
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