XRT7250 Datasheet, PDF (91/463 Pages) Exar Corporation – DS3/E3 FRAMER IC

XRT7250 DS3/E3 FRAMER IC
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REV. 1.1.1
Bit 2 - RxLAPD Enable
This Read/Write bit-field allows the user to enable or
disable the LAPD Receiver, for reception of incoming
LAPD Message frames from the Remote LAPD
Transmitter.
Writing a "1" to this bit-field enables the LAPD Re-
ceiver. Writing a "0" to this bit-field disables the LAPD
Receiver.
Bit 1 - RxLAPD (Received LAPD Message) Inter-
rupt Enable
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. For
more information on this interrupt, please see Section
5.3.3.
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 5.3.6.1.12 for a more detailed
discussion of this interrupt.
2.3.3.8 Receive E3 LAPD Status Register (E3,
ITU-T G.832
RXE3 LAPD STATUS REGISTER (ADDRESS = 0X19)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Not Used Rx ABORT
RxLAPDType[1:0]
RxCR
Type
RxFCS
Error
End of
Message
Flag
Present
RO
RO
RO
RO
R/W
R/W
R/W
RUR
0
0
0
0
0
0
0
0
Bit 6 - Rx Abort
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 - Rx CR 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 - Rx FCS 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.
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