XRT72L50 Datasheet, PDF (104/471 Pages) Exar Corporation – SINGLE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER

XRT72L50
SINGLE CHANNEL DS3/E3 FRAMER WITH HDLC CONTROLLER
REV. 1.2.1
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Bit 1 - TxLOS Enable
This Read/Write bit-field allows the user to command the Transmit E3 Framer to transmit an LOS pattern, upon
demand.
Writing a "0" to this bit-field allows the Transmit E3 Framer to transmit internally generated data (e.g., the ITU-T
G.832 compatible E3 frames with ATM cell data) to the Remote Terminal. Writing a "1" to this bit-field causes
the Transmit DS3/E3 Framer block to transmit an "All 0’s" pattern to the Remote Terminal.
NOTE: If the Transmit DS3/E3 Framer block is transmitting an LOS pattern to the RemoteTerminal, then it is not transmitting
any E3 frames. Consequently, the Remote Terminal will experience an LOS (Loss of Signal) and OOF (Out of
Frame) condition.
Bit 0 - MARx (FERF and FEBE bit-field Loop-back)
This Read/Write bit-field allows the user to specify whether the value of the FERF and FEBE bit-fields, in the
outbound E3 frames, should be based upon Receive DS3/E3 Framer conditions or upon the content of the Tx
MA Byte register (Address = 0x36).
FERF and FEBE values are based upon Receive E3 Framer Conditions
If the user selects Receive DS3/E3 Framer conditions, then the Transmit DS3/E3 Framer block will set and
clear the FERF and FEBE bit-fields in response to the following conditions.
a. FERF Bit-field
If the Receive DS3/E3 Framer block (in the same channel) is currently experiencing an LOS, AIS, or LOF
condition, then the Transmit DS3/E3 Framer block will set the FERF bit-field (in the outbound E3 frame) to "1".
Conversely, if the Receive DS3/E3 Framer block is not experiencing any of these conditions, then the Transmit
E3 Framer will set the FERF bit-field (in the outbound E3 frame) to "0".
b. FEBE bit-field
If the Receive DS3/E3 Framer block detects a BIP-8 error in the incoming E3 frame, then the Transmit DS3/E3
Framer block will set the FEBE bit-field (in the outbound E3 frame) to "1". Conversely, if the Receive DS3/E3
Framer block does not detect a BIP-8 error in the incoming E3 frame, then the Transmit DS3/E3 Framer block
will set the FEBE bit-field (in the E3 outbound E3 frame) to "0".
FEBE and FERF values are based upon the contents of the Tx MA Byte register
If the user selects the contents of the Tx MA Byte register, then whatever value has been written into bit 7
(FERF), within the Tx MA Byte register (Address = 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 Configuration 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 Receive 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.
2.3.6.2 Transmit E3 LAPD Configuration Register (E3, ITU-T G.832)
TxE3 LAPD Configuration Register (Address = 0x33)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Not Used
Auto
Retransmit
Not Used
TxLAPD
Msg Length
TxLAPD
Enable
RO
RO
RO
RO
R/W
RO
R/W
R/W
0
0
0
0
1
0
0
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-second intervals.
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