XRT7250 Datasheet, PDF (102/463 Pages) Exar Corporation – DS3/E3 FRAMER IC

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DS3/E3 FRAMER IC
XRT7250
REV. 1.1.1
This Read/Write bit-field allows the user to enable or
disable the Received LAPD Message frame interrupt.
Setting this bit-field to "1" enables this interrupt. Set-
ting this bit-field to "0" disables this interrupt.
NOTE: For more information on this interrupt, please see
Section 4.3.6.1.9.
Bit 0 - RxLAPD (Received LAPD Message) Inter-
rupt Status
This Reset-upon-Read bit-field will be set to "1" if the
Receipt of New LAPD Message frame interrupt has
occurred since the last read of this register.
The Receive E3 Framer will generate this Receipt of
New LAPD Message frame interrupt when the LAPD
Receiver has received a complete LAPD Message
frame from the Remote LAPD Transmitter.
NOTE: Please see section 4.3.6.1.9 for a more detailed dis-
cussion of this interrupt.
2.3.4.8 Receive E3 LAPD Status Register (E3,
ITU-T G.751)
RXE3 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
This Read-Only bit-field indicates whether or not the
LAPD Receiver is currently detecting an abort se-
quence (e.g., a string of 7 consecutive "1’s").
This bit-field is set to "1" if the LAPD Receiver is cur-
rently detecting an abort sequence in the incoming
LAPD Channel. Conversely, this bit-field is set to "0"
if the LAPD Receiver has not detected an abort se-
quence, since the last read of this register.
Bit 5, 4 - RxLAPD Type[1:0]
These two Read-Only bit-fields combine to indicate
the type and size of LAPD Message frame that has
been received by the LAPD Receiver. The following
table relates the contents of these bit-fields to the
LAPD Message type/size.
RXLAPDTYPE[1:0]
LAPD MESSAGE FRAME TYPE
PMDL MESSAGE SIZE (INFORMATION
SECTION)
00
Test Signal Identification Type
76 Bytes
01
Idle Signal Identification Type
76 Bytes
10
CL Path Identification Type
76 Bytes
11
ITU-T Path Identification Type
82 Bytes
Bit 3 - RxCR Type
This Read-Only bit-field indicates the state of the C/R
bit-field, within octet # 2 of the most recently received
LAPD Message frame.
Bit 2 - RxFCS Error
This Read-Only bit-field indicates whether or not the
LAPD Receiver has detected an FCS (Frame Check
Sequence) error, in the most recently received LAPD
Message frame. This bit-field is set to "0" if the LAPD
Receiver does not detect an FCS error in this LAPD
Message frame. Conversely, this bit-field is set to "1"
if the LAPD Receiver does detect an FCS error in this
LAPD Message frame.
NOTE: For a more detailed discussion on the LAPD
Receiver's handling of the FCS bytes, please see Section
4.3.3.
Bit 1 - EndOfMessage
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 con-
tains a new PMDL message that needs to be read
and processed.
This bit-field is cleared (to "0") upon reading this reg-
ister.
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