XR72L52 Datasheet, PDF (296/480 Pages) Exar Corporation – TWO CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER

XRT72L52
REV. 1.0.1
xr
TWO CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
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 XRT72L52 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.
TXE3 CONFIGURATION REGISTER (ADDRESS = 0X30)
BIT 7
Tx
BIP-4
Enable
R/W
0
BIT 6
BIT 5
TxASourceSel[1:0]
R/W
R/W
X
X
BIT 4
BIT 3
TxNSourceSel[1:0]
R/W
R/W
0
0
BIT 2
Tx AIS
Enable
R/W
0
BIT 1
Tx LOS
Enable
R/W
0
BIT 0
Tx FAS
Source
Select
R/W
0
The following table presents the relationship between the contents of TxASource[1:0] and the resulting source
of the A bit.
TXASOURCESEL[1:0]
SOURCE OF A BIT
00
TxE3 Service Bits Register (Address = 0x35)
01
Transmit Overhead Data Input Interface
10
Transmit Payload Data Input Interface
11
Functions as a FEBE (Far-End-Block Error) bit-field.
This bit-field is set to "0", if the Near-End Receive Section (within this chip) detects no BIP-4
Errors within the incoming E3 frames.
This bit-field is set to "1", if the Near-End Receive Section (within this chip) detects a BIP-4
Error within the incoming E3 frame.
Hence, if a Yellow Alarm condition needs to be transmitted to the Remote Terminal Equipment, this can be ac-
complished by executing the following steps.
STEP 1 - Write a “1” into Bit 1 (A Bit) within the Tx E3 Service Bits Register, as indicated below.
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