
PRELIMINARY
XRT79L71
218
REV. P2.0.0
1-CHANNEL DS3/E3 CLEAR-CHANNEL FRAMERLIU COMBO - CC/HDLC ARCHITECTURE
4.3.2.6.2
Clearing the FERF Defect Condition
The Receive DS3 Framer block will clear the FERF Defect Condition if it ceases to receive DS3 frames, with all
of their X bits set to "0". The Receive DS3 Framer block will indicate that it is clearing the FERF Defect
Condition by:
Setting Bit 4 (FERF Defect Declared) within the Receive DS3 Status Register to "0" as depicted below.
The Receive DS3 Framer block will also generate the Change in FERF Defect Condition interrupt, by asserting
the Interrupt Output pin (e.g., by pulling it "Low") and setting Bit 3 (Change of FERF Defect Condition Interrupt
Status), within the Receive DS3 Interrupt Status Register to "1", as illustrated below.
4.3.2.7
DETECTING P-BIT ERRORS
The Receive DS3/E3 Framer block has the responsibility for detecting and flagging the occurrences of P-bit
Errors, as described below.
Processing at the Remote Terminal Equipment
As the remote terminal is generating and transmit the incoming DS3 data-stream to the local terminal
equipment, it will compute the even parity of an entire DS3 frame. The results of this parity calculation will be
inserted into the two P-bit fields, within the very next outbound DS3 data stream. The purpose of these P-bits
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 Condi-
tion Inter-
rupt
Status
Change of
FERF Defect
Condition
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
Receive DS3 Status Register (Address = 0x1111)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Unused
FERF Defect
Declared
RxAIC
RxFEBE[2:0]
R/O
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 Condi-
tion Inter-
rupt
Status
Change of
FERF Defect
Condition
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