XRT84L38IB Exar Corporation, XRT84L38IB Datasheet - Page 342

• Manufacturer Part Number: XRT84L38IB
• Description: Network Controller & Processor ICs 8 Ch T1/E1 Framer
• Manufacturer: Exar Corporation

Specifications of XRT84L38IB

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

XRT84L38
OCTAL T1/E1/J1 FRAMER
The XRT84L38 T1/J1/E1 Octal Framer supports insertion of Robbed-bit Signaling information into the outgoing
DS1 frame. It also supports extraction and substitution of Robbed-bit Signaling information from the incoming
DS1 frame. The following section provides a brief overview of Robbed-bit Signaling in DS1 mode.
Signaling is required when dealing with voice and dial-up data services in DS1 applications. Traditionally,
signaling is provided on a dial-up telephone line, across the talk-path. Bit robbing, or stealing the least
significant bit (8th bit) in each of the twenty-four voice channels in the signaling frames allows enough bits to
signal between the transmitting and receiving end. That is how the name Robbed-bit signaling comes from.
These ends can be CPE to central office (CO) for switched services, or CPE to CPE for PBX-to-PBX
connections.
Signaling is used to tell the receiver where the call or route is destined. The signal is sent through switches
along the route to a distant end. Common types of signals are:
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•
•
•
•
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Robbed-bit Signaling is supported in three DS1 framing formats:
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In Super-Frame or SLC®96 framing mode, frame number 6 and frame number 12 are signaling frames. In
channelized DS1 applications, these frames are used to contain the signaling information. In frame number 6
and 12, the least significant bit of all twenty-four timeslots is 'robbed' to carry call state information. The bit in
frame 6 is called the A bit and the bit in frame 12 is called the B bit. The combination of A and B defines the
state of the call for the particular timeslot that these two bits are located.
In Extended Super-Frame framing mode, frame number 6, 12, 18 and 24 are signaling frames. In these
frames, the least significant bit of all twenty-four timeslots is 'robbed' to carry call state information. The bit in
frame 6 is called the A bit, the bit in frame 12 is called the B bit, the bit in frame 18 is called the C bit and the bit
in frame 24 is called the D bit. The combination of A, B, C and D defines the state of the call for the particular
timeslot that these signaling bits are located.
9.5.1
On hook
Off hook
Dial tone
Dialed digits
Ringing cycle
Busy tone
Super-Frame (SF)
SLC®96
Extended Super-Frame (ESF)
Brief Discussion of Robbed-bit Signaling in DS1 Framing Format
F
F
RAME
RAME
12
12
6
6
N
N
UMBER
UMBER
322
S
S
IGNALING
IGNALING
A
B
A
B
B
B
IT
IT
REV. 1.0.1