XRT7250 Datasheet, PDF (84/463 Pages) Exar Corporation – DS3/E3 FRAMER IC

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DS3/E3 FRAMER IC
XRT7250
2.3.2.13 Receive DS3 LAPD Control Register
RXDS3 LAPD CONTROL REGISTER (ADDRESS = 0X18)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
Not Used
RO
RO
RO
RO
RO
0
0
0
0
0
REV. 1.1.1
BIT 2
RxLAPD
Enable
R/W
0
BIT 1
RxLAPD
Interrupt
Enable
R/W
0
BIT 0
RxLAPD
Interrupt
Status
RUR
0
Bit 2 RxLAPD Enable
This Read/Write bit-field allows the user to enable or
disable the LAPD Receiver. The LAPD Receiver
MUST be enabled before it can begin to receive and
process any LAPD Message frames from the incom-
ing DS3 data stream.
Writing a "0" to this bit-field disables the LAPD Re-
ceiver (the default condition). Writing a "1" to this bit-
field enables the LAPD Receiver.
Bit 1 RxLAPD (Message Frame Reception Com-
plete) Interrupt Enable
This Read/Write bit-field allows the user to enable or
disable the LAPD Message Frame Reception Com-
plete interrupt. If this interrupt is enabled, then the
UNI will generate this interrupt to the local µP, once
the last bit of a LAPD Message frame has been re-
ceived and the PMDL message has been extracted
and written into the Receive LAPD Message buffer.
Writing a "0" to this bit-field disables this interrupt (the
default condition). Writing a "1" to this bit-field en-
ables this interrupt.
Bit 0 RxLAPD (Message Reception Complete) In-
terrupt Status
This Read-Only bit field indicates whether or not the
LAPD Message Reception Complete interrupt has
occurred since the last read of this register. The
LAPD Message Reception Complete interrupt will oc-
cur once the LAPD Receiver has received the last bit
of a complete LAPD Message frame, extracted the
PMDL message from this LAPD Message frame and
has written this (PMDL) message frame into the Re-
ceive LAPD Message buffer. The purpose of this in-
terrupt is to notify the local µP that the Receive LAPD
Message buffer contains a new PMDL message, that
needs to be read and/or processed.
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, please
see Section 3.3.3.2.
2.3.2.14 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 con-
secutive "1’s") from the far-end 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, please
see Section 3.3.3.2.
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 re-
ceived by the LAPD Receiver. The relationship be-
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