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XRT79L71
PRELIMINARY
63
1-CHANNEL DS3/E3 CLEAR-CHANNEL FRAMERLIU COMBO - CC/HDLC ARCHITECTURE
REV. P2.0.0
A repeating [1, 0, 1, 0, …] pattern is written into the payload of each DS3 frame.
The Relaxed Bellcore GR-499-CORE Compliant DS3 AIS Pattern
This particular AIS pattern has the following characteristics
Valid M-bits, F-bits and P-bits
All X-bits are set to "1"
A repeating [1, 0, 1, 0, …] pattern is written into the payload of each DS3 frame
The C-bits are NOT required to be set to "0"
The Unframed All Ones Pattern
THE DS3 IDLE CONDITION SIGNAL
The DS3 Idle Condition signal is often used to indicate that the DS3 Channel is functionally sound, but has not
yet been assigned any traffic. In other cases, the DS3 Idle pattern may be transmitted whenever a given piece
of up-stream test equipment is operating in a loop-back mode, and is performing some sort of test diagnostic
operation. The XRT79L71 can be configured to transmit and receive (detect) the following types of DS3 Idle
Patterns.
1.
The Bellcore GR-499-CORE Compliant DS3 Idle Pattern
This particular Idle pattern has the following characteristics
Valid M-bits, F-bits and P-bits
The three CP-bits within F-frame # 3 are each set to "0"
The X-bits are each set to "1"
A repeating [1, 1, 0, 0, …] pattern is written into the payload of the DS3 frames.
2.
The user-specified, unframed DS3 Idle Pattern
In this case, the user can specify an unframed 4-bit repeating pattern which can be programmed by the user as
being the DS3 Idle Pattern.
FEAC (Far-End Alarm & Control) Messages (Only available for the C-bit Parity Framing format)
The third C-bit within the first F-frame (e.g., C13 or FEAC) is used as the Far-End Alarm & Control (FEAC)
channel between the Near-End DS3 terminal and the remote DS3 terminal. The FEAC channel is typically
used to carry the following types of information.
Alarm and Status Information
Loopback commands to initiate and deactivate DS3 and DS1 loop-backs at the remote terminals.
The FEAC messages are encoded into a repeating 16-bit string that is of the following form.
Each of the dn bits can be either "1" or "0" with the rightmost bit transmitted first.
NOTE: The FEAC Message consists of a six-bit code word ([d5, d4, d3, d2, d1, d0]) which is encapsulated along with 10
framing bits to form the 16-bit FEAC Message. Since each DS3 frame carries only one FEAC bit, 16 DS3 frame
periods are required to deliver one complete FEAC Message. This six-bit code word can represent up-to 64
distinct messages, of which 43 have been defined in Bellcore GR-499-CORE. For a more detailed discussion on
FEBE (Far-End Block Error) Indicator (Only available for the C-bit Parity Framing Format)
FIGURE 19. THE BIT-FORMAT OF THE FEAC MESSAGE
0
d5
d4
d3
d2
d1
d0
0
1