XRT72L50 Datasheet, PDF (188/471 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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TABLE 28: THE RELATIONSHIP BETWEEN THE CONTENTS OF BIT 3 (TX LOS) WITHIN THE TX DS3 CONFIGURATION
REGISTER, AND THE RESULTING TRANSMIT DS3 FRAMER BLOCK'S ACTION
BIT 3
0
1
TRANSMIT DS3 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 DS3 Framer will do the following.
• Set all of the overhead bits to "0" (including the M, F, and P bits)
Overwrite the DS3 payload bits with an all zeros pattern.
NOTE: When this bit is set, it overrides all of the other bits in this register.
4.2.4.2.1.6
FERF (Far-End Receive Failure) on LOS - Bit 2
This Read/Write bit-field allows the user to configure the Transmit DS3 Framer block to automatically generate
a Yellow Alarm if the Near-End Receive Section (of the XRT72L50) detects a LOS (Loss of Signal) Condition.
Writing a "1" to this bit-field enables this feature. Writing a "0" to this bit-field disables this feature.
4.2.4.2.1.7
FERF (Far-End Receive Failure) on OOF - Bit 1
This Read/Write bit-field allows the user to configure the Transmit DS3 Framer block to automatically generate
a Yellow Alarm if the Near-End Receive Section (of the XRT72L50) detects an OOF (Out-of-Frame) Condition.
Writing a "1" to this bit-field enables this feature. Writing a "0" to this bit-field disables this feature.
4.2.4.2.1.8
FERF (Far-End Receive Failure) on AIS - Bit 0
This Read/Write bit-field allows the user to configure the Transmit DS3 Framer block to automatically generate
a Yellow Alarm if the Near-End Receive Section (of the XRT72L50) detects an AIS (Alarm Indication Signal)
pattern.
Writing a "1" to this bit-field enables this feature. Writing a "0" to this bit-field disables this feature.
4.2.4.2.1.9
Transmitting FEBE (Far-End Block Error) Values
By default, the Transmit DS3 Framer block will set the three (3) FEBE bit-fields to [1, 1, 1] if all of the following
conditions are true.
• The Local Receive DS3 Framer block detects no P-Bit Errors.
• The Local Receive DS3 Framer block detects no CP-Bit Errors
Conversely, the Transmit DS3 Framer block will set the three (3) FEBE bit-fields to a value other than [1, 1, 1] if
any one of the following conditions are true.
• The Local Receive DS3 Framer block detects a P-bit Error in the most recently received DS3 frame.
• The Local Receive DS3 Framer block detects a CP bit Error in the most recently received DS3 frame.
4.2.4.2.2
Generating Errored DS3 Frames
The Transmit DS3 Framer block permits the user to insert errors into the framing and error detection overhead
bits (e.g., the P, M and F-bits) of the outbound DS3 data stream in order to support Far-End Equipment testing.
This option can be exercised by writing data to any of the numerous Transmit DS3 Mask Registers. These
Mask Registers and their comprising bit-fields are defined below.
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