XRT72L50 Datasheet, PDF (291/471 Pages) Exar Corporation – SINGLE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER

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XRT72L50
SINGLE CHANNEL DS3/E3 FRAMER WITH HDLC CONTROLLER
REV. 1.2.1
Bit-fields 1 and 2 permit the user to transmit various alarm conditions to the remote terminal equipment. The
role/function of each of these two bit-fields within the register, are discussed below.
5.2.4.2.1.1
Tx AIS Enable - Bit 2
This read/write bit field permits the user to force the transmission of an AIS (Alarm Indication Signal) pattern to
the remote terminal equipment via software control. If the user opts to transmit an AIS pattern, then the
Transmit Section of the Framer IC will begin to transmit an unframed all ones pattern to the remote terminal
equipment. Table 51 presents the relationship between the contents of this bit-field, and the resulting Framer
action.
TABLE 51: THE RELATIONSHIP BETWEEN THE CONTENTS OF BIT 2 (TX AIS ENABLE) WITHIN THE TX E3
CONFIGURATION REGISTER, AND THE RESULTING TRANSMIT E3 FRAMER BLOCK'S ACTION
BIT 2
0
1
TRANSMIT E3 FRAMER'S ACTION
Normal Operation:
The Transmit Section of the XRT72L50 Framer IC will transmit E3 traffic based upon data that it accepts via
the Transmit Payload Data Input Interface block, the Transmit Overhead Data Input Interface block, the Trans-
mit HDLC Controller block and internally generated overhead bytes.
Transmit AIS Pattern:
The Transmit E3 Framer block will overwrite the E3 traffic, within an Unframed “All Ones” pattern.
NOTE: This bit is ignored whenever the TxLOS bit-field is set.
5.2.4.2.1.2
Transmit LOS Enable - Bit 1
This read/write bit field allows the user to transmit an LOS (Loss of Signal) pattern to the remote terminal, upon
software control. Table 52 relates the contents of this bit field to the Transmit E3 Framer block's action.
TABLE 52: THE RELATIONSHIP BETWEEN THE CONTENTS OF BIT 1 (TX LOS) WITHIN THE TX E3 CONFIGURATION
REGISTER, AND THE RESULTING TRANSMIT E3 FRAMER BLOCK'S ACTION
BIT 1
0
1
TRANSMIT E3 FRAMER'S ACTION
Normal Operation:
The Overhead bits are either internally generated, or they are inserted via the Transmit Overhead Data Input
Interface or the Transmit HDLC Controller blocks. The Payload bits are received from the Transmit Payload
Data Input Interface.
Transmit LOS Pattern:
When this command is invoked the Transmit E3 Framer will do the following.
• Set all of the overhead bytes to "0" (including the FA1 and FA2 bytes)
Overwrite the E3 payload bits with an "all zeros" pattern.
NOTE: When this bit is set, it overrides all of the other bits in this register.
5.2.4.2.1.3
Transmitting FERF (Far-End Receive Failure) Indicator or Yellow Alarm
The XRT72L50 Framer IC permits the user to control the state of the A bit-field, within each outbound E3
frame. This can be achieved by writing the appropriate data into the TxASource[1:0] bit-fields within the Tx E3
Configuration Register, as illustrated below.
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