XRT72L50 Datasheet, PDF (73/471 Pages) Exar Corporation – SINGLE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER

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XRT72L50
SINGLE CHANNEL DS3/E3 FRAMER WITH HDLC CONTROLLER
REV. 1.2.1
A "0" in this bit-field indicates that the LAPD Message Reception Complete interrupt has NOT occurred since
the last read of this register. A "1" in this bit-field indicates that the LAPD Message Reception Complete
interrupt has occurred since the last read of this register.
NOTE: For more information on the LAPD Receiver, refer to Section 4.3.3.2.
2.3.2.16 Receive DS3 LAPD Status Register
RxDS3 LAPD Status Register (Address = 0x19)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Not Used
RxAbort
RxLAPDType[1:0}
RxCR Type RxFCS Error End of Flag Present
Message
RO
RO
RO
RO
RO
RO
RO
RO
0
0
0
0
0
0
0
0
Bit 6 - RxAbort (Receive Abort Sequence)
This Read-Only bit-field indicates whether or not the LAPD Receiver has detected the occurrence of an Abort
Sequence (e.g., a string of seven or more consecutive "1’s") from the remote LAPD Transmitter. A "0" in this
bit-field indicates that no Abort-Sequence has been detected. A "1" in this bit-field indicates that the Abort-
Sequence has been detected.
NOTE: For more information on the LAPD Receiver, refer to Section 4.3.3.2.
Bits, 5 and 4 - RxLAPDType[1:0]
These two Read Only bit-fields combine to indicate the type of LAPD Message frame that has been received
by the LAPD Receiver. The relationship between these two bit-fields and the LAPD Message Type follows:
RXLAPDTYPE[1:0]
BIT 5
BIT4
0
0
0
1
1
0
1
1
MESSAGE TYPE
CL Path Identification
Idle Signal Identification
Test Signal Identification
ITU-T Path Identification
MESSAGE LENGTH
76 Bytes
76 Bytes
76 Bytes
82 Bytes
Bit 3 - RxCR (Command/Response) Type
This Read Only bit field indicates the value of the C/R (Command/Response) bit-field of the latest received
LAPD Message.
Bit 2 - Rx FCS (Frame Check Sequence) Error
This Read-Only bit-field indicates whether or not the LAPD Receiver has detected a Frame Check Sequence
(FCS) error in the most recently received LAPD Message Frame. A "0" in this bit-field indicates that the FCS
for the latest received LAPD Message Frame is correct. A "1" in this bit-field indicates that the FCS for the
latest received LAPD Message Frame is incorrect.
NOTE: For more information on the LAPD Receiver, refer to Section 4.3.3.2.
Bit 1 - End Of Message
This Read-Only bit-field indicates whether or not the LAPD Receiver has completed its reception of the latest
incoming LAPD Message frame. The local µP can poll the progress of the LAPD Receiver by periodically
reading this bit-field.
The LAPD Receiver will assert this read-only bit-field, when it has received a complete LAPD Message frame.
This bit-field, along with the Receipt of New LAPD Message frame interrupt, serves to inform the local µP that
the Receive LAPD Message buffer contains a new PMDL message that needs to be read and processed.
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