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PRELIMINARY
XRT79L71
220
REV. P2.0.0
1-CHANNEL DS3/E3 CLEAR-CHANNEL FRAMERLIU COMBO - CC/HDLC ARCHITECTURE
4.3.2.8
DETECTING CP-BIT ERRORS
The Receive DS3/E3 Framer block has the responsibility for detecting and flagging the occurrences of CP-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 three CP-bit fields, within the very next outbound DS3 data stream. The purpose of these CP-
bits is to support Path Performance Monitoring and Error Detection of the DS3 data-stream.
Processing at the Local Terminal Equipment
The Receive DS3 Framer block will compute and verify the CP-bits within each DS3 frame that it receives. If
the Receive DS3 Framer block determines that the CP-bits within a given DS3 frame are erred, then it will do
the following.
Generate the Detection of CP-bit Error interrupt request, by asserting the Interrupt Output pin (e.g., by pulling
it "Low") and setting Bit 7 (Detection of CP-Bit Error Interrupt Status), within the Receive DS3 Interrupt Status
Register, to "1" as illustrated below.
It will increment the PMON CP-bit/Parity Error Count Register once for each DS3 frame that is determined to
have a CP-bit error.
The PMON CP-bit/Parity Error Count Register is located at Address 0x1158 and
0x1159. The bit-format for these registers is presented below.
One Second - Parity Error Accumulator Register - MSB (Address = 0x1170)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
One_Second_Parity_Error_Accum_MSB[7:0]
R/O
0
One Second - Parity Error Accumulator Register - LSB (Address = 0x1171)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
One_Second_Parity_Error_Accum_LSB[7:0]
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
1
0