XRT72L50 Datasheet, PDF (292/471 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
áç
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
accomplished 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.
TxE3 Service Bits Register (Address = 0x35)
BIT 7
RO
0
BIT 6
RO
0
BIT 5
BIT 4
Not Used
RO
RO
0
0
BIT 3
RO
0
BIT 2
RO
0
BIT 1
A Bit
R/W
1
BIT 0
N Bit
R/W
0
STEP 2 - Write the value “00” into the TxASource[1:0] bit-fields within the Tx E3 Configuration Register,
as indicated below.
TxE3 Configuration Register (Address = 0x30)
BIT 7
Tx BIP-4
Enable
R/W
X
BIT 6
BIT 5
TxASourceSel[1:0]
R/W
R/W
0
0
BIT 4
BIT 3
TxNSourceSel[1:0]
R/W
R/W
X
X
BIT 2
Tx AIS
Enable
R/W
X
BIT 1
Tx LOS
Enable
R/W
X
BIT 0
Tx FAS
Source Select
R/W
X
These two steps will cause the Transmit E3 Framer block to read in the contents of Bit 1 (within the Tx E3
Service Bit register) and insert it into the A bit-field within the outbound E3 data stream. Hence, the A bit will
be set to “1”, which will be interpreted as an Alarm Condition, by the Remote Terminal Equipment.
279