![](http://datasheet.mmic.net.cn/Exar-Corporation/XRT79L71IB-F_datasheet_100145/XRT79L71IB-F_231.png)
PRELIMINARY
XRT79L71
216
REV. P2.0.0
1-CHANNEL DS3/E3 CLEAR-CHANNEL FRAMERLIU COMBO - CC/HDLC ARCHITECTURE
The Receive DS3 Framer block will also generate the Change in Idle Condition interrupt, by asserting the
Interrupt Output pin (e.g., by pulling it "Low") and setting Bit 4 (Change of Idle Condition Interrupt Status),
within the Receive DS3 Interrupt Status Register to "1", as illustrated below.
4.3.2.6
DECLARING AND CLEARING THE FERF INDICATOR
The Receive DS3/E3 Framer block has the responsibility for declaring and clearing the FERF indicator, as
described below.
4.3.2.6.1
Declaring the FERF (Far-End Receive Failure) Defect condition
The Receive DS3 Framer block will declare the FERF (Far-End-Receive Failure) or the DS3 RDI (Remote
Defect Indicator) defect condition, if it starts to receive DS3 frames with all of its X-bits set to "0".
Recall, that back in
Section 4.2.5.4, we described how one can configure the Transmit DS3/E3 Framer block to
automatically transmit the FERF indicator to the remote terminal, anytime and for the duration that the Near-
End Corresponding Receive DS3/E3 Framer Block declares either the LOS, LOF/OOF or AIS defect condition.
Figure 94 recaps some of this discussion by presenting a figure that depicts the Transmit DS3/E3 Framer
block automatically transmitting the FERF indicator to the remote terminal equipment by setting the X-bits
within each outbound DS3 frame, to "0" because the Near-End Corresponding Receive DS3 Framer block was
declaring the LOS condition.
Receive DS3 Configuration and Status Register (Address = 0x1110)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
RxAIS
Defect
Declared
RxLOS
Defect
Declared
RxIdle
Condition
Declared
RxOOF
Defect
Declared
Unused
Framing with
Valid P-Bits
F-Sync Algo
M-Sync Algo
R/O
R/W
0
Receive DS3 Interrupt Status Register (Address = 0x1113)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Detection of
CP Bit Error
Interrupt
Status
Change of
LOS Defect
Condition
Interrupt
Status
Change of
AIS Defect
Condition
Interrupt
Status
Change of
Idle
Condition
Interrupt
Status
Change of
FERF Defect
Interrupt
Status
Change of
AIC State
Interrupt
Status
Change of
OOF Defect
Condition
Interrupt
Status
Detection of
P-Bit Error
Interrupt
Status
RUR
0
1
0