XRT72L56 Datasheet, PDF (208/486 Pages) Exar Corporation – SIX CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER

XRT72L56 SIX CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
REV. P1.1.2
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PRELIMINARY
• Generate and transmit a desired value for FEBE
(Far-End-Block Error).
The procedure and results of generating any of these
alarm conditions is presented below.
The user can exercise each of these options by writ-
ing the appropriate data to the Tx DS3 Configuration
Register (Address = 0x30). The bit format of this reg-
ister is presented below.
TX DS3 CONFIGURATION REGISTER (ADDRESS = 0X30)
BIT 7
BIT 6
BIT 5
BIT 4
Tx
Yellow Alarm
R/W
0
Tx X-Bit
R/W
0
Tx IDLE
Pattern
R/W
1
Tx AIS
Pattern
R/W
0
The role/function of each of these bit-fields within the
register, are discussed below.
4.2.4.2.1.1 Transmit Yellow Alarm - Bit 7
This read/write bit field permits the user to force the
transmission of a Yellow Alarm to the remote terminal
BIT 3
BIT2
BIT 1
BIT 0
Tx LOS
Pattern
R/W
1
FERF on
LOS
R/W
0
FERF on
OOF
R/W
1
FERF on
AIS
R/W
1
equipment via software control. If the user opts to
transmit a Yellow Alarm then both of the X-bits, within
the outbound DS3 frames will be set to '0'. Table 28
relates the content of this bit field to the Transmit DS3
Framer block's action.
TABLE 28: THE RELATIONSHIP BETWEEN THE CONTENTS OF BIT 7 (TX YELLOW ALARM) WITHIN THE TX DS3
CONFIGURATION REGISTER, AND THE RESULTING TRANSMIT DS3 FRAMER BLOCK'S ACTION
BIT 7
0
1
TRANSMIT DS3 FRAMER'S ACTION
Normal Operation:
The X-bits are generated by the Transmit DS3 Framer block based upon Near End Receiving Conditions (as
detected by the Receive Section of the chip)
Transmit Yellow Alarm:
The Transmit DS3 Framer block will overwrite the X-bits by setting them all to 0. The payload information is
not modified and is transmitted as normal.
NOTE: This bit is ignored when either the TxIDLE, TxAIS, or
the TxLOS bit-fields are set.
4.2.4.2.1.2 Transmit X-bit - Bit 6
This bit field functions as the logical complement to
Bit 7 (e.g., Tx Yellow Alarm). This read/write bit field
permits the user to force all of the X-bits, in the out-
bound DS3 frames, to "1" and transmit them to the re-
mote terminal equipment. Table 29 relates the con-
tent of this bit field to the Transmit DS3 Framer
Block's action.
TABLE 29: THE RELATIONSHIP BETWEEN THE CONTENTS OF BIT 6 (TX X-BITS) WITHIN THE TX DS3 CONFIGURATION
REGISTER, AND THE RESULTING TRANSMIT DS3 FRAMER BLOCK'S ACTION
BIT 6
0
1
TRANSMIT DS3 FRAMER'S ACTION
Normal Operation:
The X-bits are generated by the Transmit DS3 Framer block based upon Receiving Conditions (as detected
by the Receive Section of the Framer chip).
Set X-bits to 1:
The Transmit DS3 Framer will overwrite the X-bits by setting them to 1. Payload information is not modified
and is transmitted as normal.
NOTE: This bit is ignored when either the Transmit Yellow
Alarm, Tx AIS, Tx IDLE, or TxLOS bit is set.
4.2.4.2.1.3 Transmit Idle Pattern - Bit 5
This read/write bit field permits the user to transmit an
Idle pattern to the remote terminal equipment upon
software control. Table 30 relates the contents of this
bit field to the Transmit DS3 Framer's action.
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