Software Procedures Related to RS232 HW Lines
B-6 AT Commands Reference Manual June 30, 2008
UIH Frames
Unnumbered information (UIH) frames contain only a Header checksum. There are two types of
UIH frames:
•Data transfer frames destined to a specific IDLC channel. The G24 MUX distributes the data
inside the UIH frame to the relevant IDLC.
•Control frames being sent between the two MUX control channels. Upon receiving a UIH
frame, the G24 acknowledges by by sending back the same frame to the DTE with the c/r bit
changed.
Test UIH Control Frames
Upon receiving a Test frame, the G24 sends back a test frame response to the DTE. This test
mechanism lets the DTE "know" that the G24 MUX is communicating.
MSC UIH Control Frame – Virtual Channel V.24 signals
The MSC frame reflects the current IDLC v.24 signal status. The G24 stores eight statuses for
each established IDLC. The signals are divided into two groups:
•M_FC, RI, DCD, CTS, DSR
•D_FC, RTS, DTR
DISC0 Reception – Close
MUX Upon receiving a DISC0 frame, the G24 checks for any open IDLCs. If
the only open channel is the control channel, the G24 sends a UA frame
to the DTE, returns to PREMUX state (command mode) and sends an
OK to the DTE.
If there are any open information channels, or if the G24 cannot return to
PREMUX state, it sends a DM frame to the DTE.
Note:
After opening the MUX, it should remain open until the G24 is
powered down. A close procedure is also supported on the MUX,
which enables you to close the MUX, return to PREMUX, and
then open the MUX again. Because of this basic concept, you
should avoid programming DTE applications to open and close the
G24 MUX frequently.
CLD Command – Close
Down Upon receiving a CLD frame, the G24 checks whether there are any
open IDLC frames. If the only open channel is the control channel, the
G24 sends a UA frame to the DTE, returns to PREMUX state (command
mode) and sends an OK to the DTE.
If there are any open information channels, or if the G24 cannot return to
PREMUX state, it sends a DM frame to the DTE.
Note:
This option will be supported in future releases.
MSC Command If "FC" bit in MSC command is set, G24 MUX stops to send data on a
corresponding to a DLCI field virtual channel.
Otherwise G24 MUX starts to send data on a corresponding to a DLCI
field virtual channel.
The G24 MUX replies to a terminal with received MSC command.
Table B-3:MUX State Procedures (Cont.)
Procedure Description