XRT86L30
SINGLE T1/E1/J1 FRAMER/LIU COMBO
REV. 1.0.1
6.3
Programming Sequence for Receiving LAPD Messages
The XRT86L30 can extract data link information from incoming DS1 frames from either the datalink bits
themselves or the D/E time slots within the PCM input data. To extract a LAPD message, the following
programming sequence can be used as a reference.
1. Enable RxEOT in the Data Link Interrupt Enable Register.
2. Wait for the RxEOT interrupt to occur.
3. Once RxEOT occurs, read the Receive Data Link Byte Count Register to determine which buffer the data is
extracted to and how many bytes are contained within the message.
4. Read the exact amount of bytes from the proper buffer. If buffer 0, read 0x0600. If buffer 1, read 0x0700. These
two registers are automatically incremented.
6.4
SS7 (Signaling System Number 7) for ESF in DS1 Only
To support SS7 specifications while receiving LAPD messages, EXAR’s Framer will generate an interrupt (if
SS7 is enabled) once the HDLC controllers have received more than 276 bytes within two flag sequences
(0x7E) of a LAPD message. Each HDLC controller supports SS7. For example: To enable SS7 for all HDLC
controllers, registers 0x0B11 (LAPD1), 0x0B19 (LAPD2), 0x0B29 (LAPD3) must be set to 0x01.
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EXAR [ EXAR CORPORATION ]
