XR72L52 Datasheet, PDF (352/480 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
current state of the AIS defect by reading the state of Bit 3 (RxAIS) within the Rx E3 Configuration and Sta-
tus Register - 2, as illustrated below.
RXE3 CONFIGURATION & STATUS REGISTER - 2 (ADDRESS = 0X11)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
RxLOF
Algo
RxLOF
RxOOF
RxLOS
RxAIS
Not Used
RxFERF
R/W
RO
RO
RO
RO
RO
RO
RO
0
1
1
0
0
1
1
1
If the AIS Condition is TRUE
1. It should begin transmitting the FERF indication to the Remote Terminal Equipment. Please see
Section 5.2.4.2.1.3.
If the AIS Condition is FALSE
2. It should cease transmitting the FERF indication to the Remote Terminal Equipment.
NOTE: The device cannot be configured to automatically send/clear FERF on LOS, LOOf, OOF or AIS in E3 G.751 mode.
The user must implemt it in the ISR.
Please see Section 5.2.4.2.1.3 for instructions on how to control the state of the A bit-field, within each out-
bound E3 frame.
5.3.6.2.5 The Change of Framing Alignment Interrupt
If the Change of Framing Alignment Interrupt is enabled then the XRT72L52 Framer IC will generate an inter-
rupt any time the Receive E3 Framer block detects an abrupt change of framing alignment.
NOTE: This interrupt is typically accompanied with the Change in Receive OOF Condition interrupt as well.
Conditions causing the XRT72L52 Framer IC to generate this interrupt.
If the XRT72L52 Framer detects receives at least four consecutive E3 frames, within its Framing Alignment
bytes in Error, then the XRT72L52 Framer IC will declare an OOF condition. However, while the XRT72L52
Framer IC is operating in the OOF condition, it will still rely on the old framing alignment for E3 payload data
extraction, etc.
However, if the Receive E3 Framer had to change alignment, in order to re-acquire frame synchronization,
then this interrupt will occur.
Enabling and Disabling the Change of Framing Alignment Interrupt
The user can enable or disable the Change of Framing Alignment Interrupt by writing the appropriate value into
Bit 4 (COFA Interrupt Enable), within the Rx E3 Interrupt Enable Register - 1.
RXE3 INTERRUPT ENABLE REGISTER - 1 (ADDRESS = 0X12)
BIT 7
BIT 6
Not Used
BIT 5
RO
RO
RO
0
0
0
BIT 4
COFA
Interrupt
Enable
R/W
X
BIT 3
OOF
Interrupt
Enable
R/W
0
BIT 2
LOF
Interrupt
Enable
R/W
0
BIT 1
LOS
Interrupt
Enable
R/W
0
BIT 0
AIS
Interrupt
Enable
R/W
0
Writing a “1” into this bit-field enables the Change of Framing Alignment Interrupt. Conversely, writing a “0” into
this bit-field disables the Change of Framing Alignment Interrupt.
Servicing the Change of Framing Alignment Interrupt
Whenever the XRT72L52 Framer IC generates this interrupt, it will do the following.
336