XRT72L50 Datasheet, PDF (420/471 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
• Setting Bit 4 (RxLOS) of the Rx E3 Configuration & Status Register to “1” as depicted below.
RxE3 Configuration & Status Register 2 (Address = 0x11)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Rx LOF Algo RxLOF
RxOOF
RxLOS
RxAIS
RxPld Unstab
Rx
TMark
RxFERF
R/W
RO
RO
RO
RO
RO
RO
RO
0
0
0
1
0
0
0
0
• The Receive E3 Framer block will generate a Change in LOS Condition interrupt request. Upon generating
this interrupt request, the Receive E3 Framer block will assert Bit 1 (LOS Interrupt Status within the Rx E3
Framer Interrupt Status Register - 1, as depicted below.
RxE3 Interrupt Status Register - 1 (Address = 0x14)
BIT 7
BIT 6
Not Used
BIT 5
RO
RO
RO
0
0
0
BIT 4
COFA
Interrupt
Status
RUR
0
BIT 3
OOF
Interrupt
Status
RUR
0
BIT 2
LOF
Interrupt
Status
RUR
0
BIT 1
LOS
Interrupt
Status
RUR
1
BIT 0
AIS
Interrupt
Status
RUR
0
Clearing the LOS Condition
The Receive E3 Framer block will clear the LOS condition when it encounters a stream of 32 bits that does not
contain a string of 4 consecutive zeros or if the ExtLOS pin goes low.
When the Receive E3 Framer block clears the LOS condition, then it will notify the Microprocessor and the
external circuitry of this occurrence by:
• Generating the Change in LOS Condition Interrupt to the Microprocessor.
• Clearing Bit 4 (RxLOS) within the Rx E3 Configuration & Status Register, as depicted below.
RxE3 Configuration & Status Register 2 (Address = 0x11)
BIT 7
Rx LOF Algo
BIT 6
RxLOF
R/W
RO
0
0
BIT 5
RxOOF
RO
0
BIT 4
RxLOS
RO
0
BIT 3
RxAIS
RO
0
BIT 2
RxPld Unstab
RO
0
BIT 1
Rx
TMark
RO
0
BIT 0
RxFERF
RO
0
• Clear the RxLOS output pin (e.g., toggle it "Low”).
6.3.2.6.2
The AIS (Alarm Indication Status) Condition
Declaring the AIS Condition
The Receive E3 Framer block will identify and declare an AIS condition, if it detects an “All Ones” pattern in the
incoming E3 data stream. More specifically, the Receive E3 Framer block will declare an AIS Condition if 7 or
less “0s” are detected in each of 2 consecutive E3 frames.
If the Receive E3 Framer block declares an AIS Condition, then it will do the following.
407