XRT72L56 Datasheet, PDF (127/486 Pages) Exar Corporation – SIX CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER

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SIX CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
XRT72L56
REV. P1.1.2
2Ah), will be the value of the FERF bit-field, in the
outbound E3 frame. Likewise, whatever value has
been written into Bit 6 (FEBE) within the Tx MA Byte
register, will be the value of the FEBE bit-field, in the
outbound E3 frame.
Writing a "1" into Bit 0 (MAx) within the Tx E3 Config-
uration register configures the Transmit DS3/E3
Framer block to set the FERF and FEBE bit-fields (in
the outbound E3 frames) to values based upon Re-
ceive E3 Framer conditions. Writing a "0" into this bit-
field configures the Transmit DS3/E3 Framer block to
set the FEBE and FEBE bit-fields (in the outbound E3
frames) to the values written into bit-fields 6 and 7
within the Tx MA Byte register.
2.4.6.2 Transmit E3 LAPD Configuration Reg-
ister (E3, ITU-T G.832)
TXE3 LAPD CONFIGURATION REGISTER (ADDRESS = 0X33)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
Not Used
Auto
Retransmit
RO
RO
RO
RO
R/W
0
0
0
0
1
BIT 2
Not Used
RO
0
BIT 1
TxLAPD
Msg Length
R/W
0
BIT 0
TxLAPD
Enable
R/W
0
Bit 3 - Auto Retransmit
This Read/Write bit-field permits the user to configure
the LAPD Transmitter to either transmit the LAPD
Message frame only once, or repeatedly at one-sec-
ond intervals.
Writing a "0" to this bit-field configures the LAPD
Transmitter to transmit the LAPD Message frame
once. Afterwards, the LAPD Transmitter will halt
transmission, until it has commanded to transmit an-
other LAPD Message frame.
Writing a "1" to this bit-field configures the LAPD
Transmitter to transmit the LAPD Message frame re-
peatedly at One-Second intervals. In this configura-
tion, the LAPD Transmitter will repeat its transmission
of the LAPD Message frame until it has been dis-
abled.
Bit 1 - TxLAPD Message Length Select
This Read/Write bit-field permits the user to select
the length of the outbound LAPD Message frame.
Setting this bit-field to "0" configures the outbound
LAPD Message frame to be 76 bytes in length. Set-
ting this bit-field to "1" configures the outbound LAPD
Message frame to be 82 bytes in length.
Bit 0 - TxLAPD Enable
This Read/Write bit-field permits the user to enable or
disable the LAPD Transmitter. The LAPD Transmitter
must be enabled before it can be commanded to
transmit a LAPD Message frame (containing a PMDL
message) via the outbound E3 frames, to the Remote
Terminal.
Writing a "0" disables the LAPD Transmitter (default
condition). Writing a "1" enables the LAPD Transmit-
ter.
NOTE: For information on the LAPD Transmitter, please see
Section 3.2.3.2.
2.4.6.3 Transmit E3 LAPD Status and Interrupt
Register (E3, ITU-T G.832)
TXE3 LAPD STATUS AND INTERRUPT REGISTER (ADDRESS = 0X34)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Not Used
TxDL Start TxDL Busy
TxLAPD
Interrupt
Enable
TxLAPD
Interrupt
Status
RO
RO
RO
RO
R/W
RO
R/W
RUR
0
0
0
0
0
0
0
0
Bit 3 - TxDL Start
This Read/Write bit-field permits the user to com-
mand the LAPD Transmitter to do the following.
• Scan through the PMDL Message, within the Trans-
mit LAPD Message buffer, and search for a string of
five (5) consecutive "1’s". The LAPD Transmitter
will then insert (or stuff) a "0" into the PMDL Mes-
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