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DS3171/DS3172/DS3173/DS3174
107
Immediately after a reset (or datapath reset) or a LOS condition, a BPV will not be declared when the first valid one
(RPOS high and RNEG low, or RPOS low and RNEG high) is received. Bipolar to unipolar conversion converts the
AMI bipolar data into a unipolar signal by ORing together the RXP and RXN signals.
10.11 BERT
10.11.1 General Description
The BERT is a software programmable test pattern generator and monitor capable of meeting most error
performance requirements for digital transmission equipment. It will generate and synchronize to pseudo-random
patterns with a generation polynomial of the form x
n
+ x
y
+ 1, where n and y can take on values from 1 to 32 and to
repetitive patterns of any length up to 32 bits.
The transmit direction generates the programmable test pattern, and inserts the test pattern payload into the data
stream.
The receive direction extracts the test pattern payload from the receive data stream, and monitors the test pattern
payload for the programmable test pattern. See
for the location of the BERT Block within the
DS3174x devices.
Figure 10-28. BERT Block Diagram
DS3/E3
Transmit
LIU
IEEE P1149.1
JTAG Test
Access Port
Microprocessor
Interface
HDLC
FEAC
LLB
DLB
DS3 / E3
Transmit
Formatter
DS3 / E3
Receive
Framer
Trail
Trace
Buffer
DS3/E3
Receive
LIU
TAIS
TUA1
Clock Rate
Adapter
TX BERT
RX BERT
PLB
ALB
UA1
GEN
B3ZS/
HDB3
Encoder
B3ZS/
HDB3
Decoder
10.11.2 Features
•
Programmable PRBS pattern
– The Pseudo Random Bit Sequence (PRBS) polynomial (x
n
+ x
y
+ 1) and seed
are programmable (length n = 1 to 32, tap y = 1 to n - 1, and seed = 0 to 2
n
- 1).
•
Programmable repetitive pattern
– The repetitive pattern length and pattern are programmable (the length n
= 1 to 32 and pattern = 0 to 2
n
- 1).
•
24-bit error count and 32-bit bit count registers
•
Programmable bit error insertion
– Errors can be inserted individually, on a pin transition, or at a specific
rate. The rate 1/10
n
is programmable (n = 1 to 7).
•
Pattern synchronization at a 10
-3
BER
– Pattern synchronization will be achieved even in the presence of a
random Bit Error Rate (BER) of 10
-3
.
10.11.3 Configuration and Monitoring
Set
PORT.CR1
.BENA = 1 to enable the BERT. The BERT must be enabled before the pattern is loaded for the
pattern load operation to take affect.
The following tables show how to configure the on-board BERT to send and receive common patterns.