XRT86L30
REV. 1.0.1
SINGLE T1/E1/J1 FRAMER/LIU COMBO
6.5
DS1/E1 Datalink Transmission Using the HDLC Controllers
The transmit framer block can insert data link information to outbound DS1/E1 frames. The data link
information can be inserted from the following sources.
•
•
Transmit Overhead Input Interface (TxOH)
Transmit HDLC1 Controller
•
Transmit Serial Input Interface (TxSER)
NOTE: HDLC1 is the dedicated controller for transmission of LAPD messages through the datalink bits. If the datalink bits
are not used for LAPD messages, then HDLC1 can be used through the D/E time slots as with HDLC2 and HDLC3.
The Transmit Data Link Source Select bits within the Transmit Data Link Select Register (TSDLSR) determine
the source for the data link bits in ESF, SLC®96, or T1DM for DS1 and CRC multi frame for E1. Each Transmit
HDLC Controller contains four major functional modules.
•
•
•
•
Bit-Oriented Signaling Processor
LAPD Controller
SLC®96 Data Link Controller
Automatic Performance Report (APR) Generation
6.6
Transmit BOS (Bit Oriented Signaling) Processor
The Transmit BOS Processor handles transmission of BOS messages through the data link channel. The
processor can be set for a specific amount of repetitions a certain BOS message will be transmitted, or it may
be placed in an infinite loop. The processor can also insert a BOS IDLE flag sequence and/or an ABORT
sequence to be transmitted on the data link channel.
6.6.1
Description of BOS
Bit-Oriented Signaling messages are a 16-bit pattern of which a 6-bit message is embedded as shown in the
following table.
BOS MESSAGE
FORMAT
0
D5
D4
D3
D2
D1
D0
0
1
1
1
1
1
1
1
1
Where D5 is the MSB and D0 is the LSB. The rightmost "1" is transmitted first. BOS is classified into the
following two groups.
•
•
Priority Codeword Message
Command and Response Information
6.6.2
Priority Codeword Message
A Priority Codeword Message is preemptive and has the highest priority among all data link information. A
Priority Codeword indicates a condition that is affecting the quality of service and thus shall be transmitted until
the condition no longer exists. The duration of transmission should not be less than one second. A priority
codeword may be interrupted by software for 100 milliseconds to send maintenance commands with a
minimum interval of one second between interruptions. Yellow alarm (00000000 11111111) is the only priority
message defined in industry standards.
6.6.3
Command and Response Information
Command and Response Information is transmitted to perform various functions. The BOS Processor can
send a command and response by transmitting a minimum of 10 repetitions of the appropriate codeword
pattern. A Command and response data transmission initiates action at the remote end, while the remote end
will respond by sending Bit-Oriented response message to acknowledge the received commands. The
activation and deactivation of line remote loop-back and local payload loop-back functions are of this type.
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EXAR [ EXAR CORPORATION ]
