XRT7250 Datasheet, PDF (112/463 Pages) Exar Corporation – DS3/E3 FRAMER IC

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DS3/E3 FRAMER IC
XRT7250
REV. 1.1.1
TXE3 MA BYTE REGISTER (ADDRESS = 0X36)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
Transmit MA Byte
FERF
FEBE
Payload Type
R/W
R/W
R/W
R/W
R/W
0
0
0
1
0
BIT 2
BIT 1
Payload Dependent
R/W
R/W
0
0
BIT 0
Timing
Marker
R/W
0
This Read/Write byte-fields allows the user to specify
the contents of the MA byte-field in each outbound E3
frame.
NOTE: The values written into bit-fields 6 (FEBE) and 7
(FERF) are inserted into outbound E3 frames, only if bit-
field 0 (MAx) within the Tx E3 Configuration Register
(Address = 28h) is set to "0". Otherwise, the Transmit E3
Framer will set the FERF and FEBE values, within each
outbound E3 frame, to values based upon Receive E3
Framer conditions.
2.3.6.6 Transmit E3 NR Byte Register (E3, ITU-
T G.832)
TXE3 NR BYTE REGISTER (ADDRESS = 0X37)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
TxNR[7:0]
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
1
0
0
0
0
This Read/Write byte-field allows the user to specify
the contents of the NR byte-field in each outbound E3
frame.
NOTE: The contents of this register is ignored, if the LAPD
Transmitter is enabled and has been configured to insert
the comprising octets of an outbound LAPD Message
frame into the NR byte-field of each outbound E3 frame
(e.g., if DLinNR = "1").
2.3.6.7 Transmit E3 TTB-0 Register (E3, ITU-T
G.832)
TXE3 TTB-0 REGISTER (ADDRESS = 0X38)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
TxTTB0[7:0]
R/W
R/W
R/W
R/W
R/W
1
0
0
1
0
BIT 2
R/W
0
BIT 1
R/W
0
BIT 0
R/W
0
This Read/Write byte-field, along with the Tx TTB-1
through Tx TTB-15 registers allows a user to define a
Trail Access Point Identifier sequence of bytes, that
will be transmitted to the Far-End Terminal. The Far-
End Receiving Terminal will use this sequence of
bytes to verify that it is connected to the proper Trans-
mitting Terminal. The Transmit E3 Framer will take
the contents of these 16 registers, and insert them in-
to the TR byte of the outbound E3 frame. In the first
of a set of 16 E3 Frames, the Transmit E3 Framer will
read in the contents of this register, and insert it into
the TR byte-field, within the very next outbound E3
frame.
This particular byte-field should contain the pattern
"[1, C6, C5, C4, C3, C2, C1, C0]" where C6 through
C0 are the results of a CRC-7 calculation over the
previous 16-byte frame.
NOTE: The XRT7250 Framer IC will not compute this CRC-
7 value. It is up to the user's hardware and/or software to
compute this value, prior to writing it into this register.
2.3.6.8 Transmit E3 TTB-1 Register (E3, ITU-T
G.832)
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