XRT84L38IB Exar Corporation, XRT84L38IB Datasheet - Page 195

• 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

REV. 1.0.1
A single T1 frame is 193 bits long and is transmitted at a frame rate of 8000Hz. This results in an aggregate bit
rate of 193 bits X 8000/sec = 1.544 Mbits/sec. Basic frames are divided into 24 timeslots numbered 1 thru 24
and a framing bit, see
numbered bit 0. This results in a single timeslot data rate of 8 bits x 8000/sec = 64 kbits/sec.
The Superframe Format (SF), is also referred to as the D4 format. The requirement for associated signaling in
frames 6 and 12 dictates that the frames be distinguishable. This leads to a multiframe structure consisting of
12 frames per superframe (SF). See
The SF structure consists of a multiframe of 12 frames. Each frame has 24 timeslots, plus an F-bit and 8 bits
per timeslot. A timeslot is equivalent to one voice circuit or one 64kb/s data circuit.
This structure of frames and multiframes is defined by the F-bit pattern. The F-bit is designated alternately as
an Ft bit (terminal framing bit) or Fs bit (signalling framing bit). The Ft bit carries a pattern of alternating zeros
and ones (101010) in odd frames that defines the boundaries so that one timeslot may be distinguished from
another. The Fs bit carries a pattern of (001110) in even frames and defines the multiframe boundaries so that
one frame may be distinguished from another.
F
3.0 THE DS1 FRAMING STRUCTURE
3.1
IGURE
Timeslot
20. T1 F
24
T1 Super Frame Format (SF)
(1/1.544)μs
RAME
bit
S
Figure 20
F
Timeslot
ORMAT
1
. Each timeslot is 8 bits in length and is transmitted most significant bit first,
Figure 21
Timeslots
Bit 0
2 - 22
DS1 Frame
Bit 0
125μs
and
Bit 1
Table 33
Bit 1
175
Bit 2
Bit 2
.
(8/1.544)μs
Bit 3
Timeslot
Bit 3
23
Bit 4
Bit 4
Bit 5
Timeslot
Bit 5
24
OCTAL T1/E1/J1 FRAMER
Bit 6
Bit 6
Bit 7
bit
S
Bit 7
Timeslot
XRT84L38
1