xr
PRELIMINARY
XRT86VL38
REV. P1.0.6
OCTAL T1/E1/J1 FRAMER/LIU COMBO
414
13.2.2
CAS Multi-Frames and Channel Associated Signaling
CAS Multi-Frames are only relevant if the user is using CAS or Channel Associated Signaling. If the user is
implementing Common Channel Signaling then the CAS Multi-Frame is not available.
13.2.2.1
Channel Associated Signaling
If the user operates an E1 channel in Channel Associated Signaling, then timeslot 16 octets within each E1
frame will be reserved for signaling. Such signaling would convey information such as On-Hook, Off-Hook
conditions, call set-up, control, etc. In CAS, this type of signaling data that is associated with a particular voice
channel will be carried within timeslot 16 of a particular E1 frame within a CAS Multi-Frame. The CAS is
carried in a Multi-Frame structure which consists of 16 consecutive E1 frames. The framing/byte format of a
CAS Multi-Frame is presented in Figure 111.
Timeslot 16 within frame 0 is a special octet that is used to convey CAS Multi-Frame alignment information,
and to convey Multi-Frame alarm information to the Remote Terminal. The bit-format of timeslot 16 within
frame 0 of a CAS Multi-Frame is 0000 xyxx. The upper nibble of this octet contains all zeros and is used to
identify itself as the CAS Multi-Frame alignment signal. If CAS is used, then the user is advised to insure that
none of the other timeslot 16 octets contain the value "0000". The lower nibble of this octet contains the
expression "xyxx". The x-bits are the spare bits and should be set to "0" if not used. The y-bit is used to
indicate a Multi-Frame alarm condition to the Remote terminal. During normal operation, this bit-field is
cleared to "0". However, if the Local Receive E1 Framer detects a problem with the incoming Multi-Frames,
then the Local Transmit E1 Framer will set this bit-field within the next outbound CAS Multi-Frame to "1".
N
OTE
: The Local Transmit E1 Framer will continue to set the y-bit to "1" for the duration that the Local Receive E1 Framer
detects this problem.
Timeslot 16 within Frame 1 of the CAS Multi-Frame contains 4 bits of signaling data for voice channel 1 and 4
bits of signaling data for voice channel 17. Timeslot 16 within Frame 2 contains 4 bits of signaling data for
voice channel 2 and 4 bits of signaling data for voice channel 18, and this continues for all E1 frames.
F
IGURE
111. F
RAME
/B
YTE
F
ORMAT
OF
THE
CAS M
ULTI
-F
RAME
S
TRUCTURE
Frame 0
Frame 1
Frame 2
Frame 15
0000
xyxx
Timeslot 16
Timeslot 16
Timeslot 16
Timeslot 16
ABCD
ABCD
Signaling Data
Associated with
Timeslot 1
Signaling Data
Associated with
Timeslot 17
ABCD
ABCD
ABCD
ABCD
CAS Multiframe
Alignment Pattern
x = “dummy bits”
y = Carries the Multiframe “Yellow Alarm” bit
Signaling Data
Associated with
Timeslot 2
Signaling Data
Associated with
Timeslot 18
Signaling Data
Associated with
Timeslot 15
Signaling Data
Associated with
Timeslot 31
A Single CAS Multiframe