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XRT79L71
PRELIMINARY
523
1-CHANNEL DS3/E3 CLEAR-CHANNEL FRAMERLIU COMBO - CC/HDLC ARCHITECTURE
REV. P2.0.0
a. Asserting the Interrupt Request output pin (INT*), by pulling it "Low".
b. Setting Bits 2 (Change in LOF Defect Condition Interrupt Status) and 3 (Change in OOF Defect
Condition Interrupt Status) within the Receive E3 Interrupt Status Register # 1 to "1" as depicted below.
When the Receive E3 Framer block is operating in the In-Frame state, it will then begin to perform Frame
Maintenance operations, where it will continue to verify that the Framing Alignment Octets FA1 and FA2 are
present at their proper locations, within the incoming E3 data-stream. In general, as long as the FA1 and FA2
bytes are present at their proper locations, with a small number of errors the Receive E3 Framer block will
continue to operate in the Frame Maintenance Mode. However, if this Receive E3 Framer block begins to
detect a large number of FA1 and FA2 byte errors within the incoming E3 data-stream, then it will exit the In-
Frame state and will then declare the OOF defect condition whenever the Receive E3 Framer block receives at
least four (4) consecutive E3 frames, in which the FA1 or FA2 bytes were erred.
Forcing a Reframe via Software Command
The Receive DS3/E3 Framer block permits the user to command a reframe procedure with the Receive E3
Framer block via software command. The user can accomplish this by inducing a 0 to 1 transition in Bit 0
(Reframe), within the I/O Control Register as depicted below. Once the user executes this step, then the
Receive E3 Framer block will be forced into the Frame Acquisition Mode or more specifically, in the FA1, FA2
Octet Search State, per Figure 248, and will begin to search for the FA1 and FA2 bytes. The XRT79L71 will
also respond to this command by declaring both the OOF and LOF Defect Conditions, and by generating the
Change in OOF Defect Condition and the Change in the LOF Defect Condition interrupts.
NOTE: After the user has implemented the 0 to 1 transition within Bit 0 (Reframe), the user should also go back and induce
a 1 to 0 transition within this bit-field.
6.3.2.3
DECLARING AND CLEARING THE LOS DEFECT CONDITION
The Receive E3 Framer block has the responsibility for declaring and clearing the LOS (Loss of Signal) defect
condition, within the incoming E3 data-stream, as described below.
6.3.2.3.1
Declaring the LOS Defect Condition
The Receive E3 Framer block will declare the Loss of Signal (LOS) Defect condition when it detects at least 32
consecutive "0s" within the incoming E3 data-stream, or if the Receive DS3/E3 LIU Block declares the LOS
defect condition. The Receive E3 Framer block will indicate that it is declaring the LOS defect condition by
doing all of the following.
Receive E3 Interrupt Status Register # 1 - G.832 (Direct Address = 0x1114)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Unused
Change in
SSM MSG
Interrupt
Status
Change in
SSM OOS
Interrupt
Status
COFA
Interrupt
Status
Change in
OOF Defect
Condition
Interrupt
Status
Change in
LOF Defect
Condition
Interrupt
Status
Change in
LOS Defect
Condition
Interrupt
Status
Change in
AIS Defect
Condition
Interrupt
Status
R/O
RUR
0
1
0
I/O Control Register (Address = 0x1101)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Disable
TxLOC
LOC
Disable
RxLOC
Unused
Reframe
R/W
R/O
R/W
R/O
R/W
1
0
1
0
1
0
0 -> 1