Multi-Service Access Device For Channelized Interfaces
Telecom Standard Product Data Sheet
Production
Proprietary and Confidential to PMC-Sierra, Inc., and for its Customers’ Internal Use
Document ID: PMC-1990823, Issue 4
593
14.22.5 Error Detection and Accumulation
By comparing the received PRBS byte with the calculated PRBS byte, the monitor is able to
detect byte errors in the payload. A byte error is detected on a comparison mismatch of the two
bytes. Only a single byte error is counted regardless of the number of errored bits in the byte. All
byte errors are accumulated in a 16 bit byte error counter. The error counter will saturate at its
maximum value of FFFFh, ie it will not wrap around to 0000h if further PRBS byte errors are
encountered. The counter is readable via the PRGM Monitor Error Count. An indirect read to that
register will initiate a transfer of the error counter into the registers for reading. The error counter
is cleared when transferred into the registers and the accumulation restarts at zero. When reading
error counts for concatenated payloads of STS-3c /STM-1c or STS-12c/STM-3c sizes, it is only
necessary to read the error count in the master slice (first associated STS-1).
All counts will be accumulated in the master slice when the error count transfer is initiated. In the
case of STS-48c/STM-16c payloads, it is necessary to read the error count in the first STS-1 of
each PRGM in the group of 4 PRGMs associated with the STS-48c/STM-16c monitor.
Alternately, all STS-1 error counts belonging to a concatenated stream may be read. In this case,
the error counts in each associated register must be summed by software. For each independent
STS-1 monitored by a PRGM, the error count register for each individual STS-1 must be read.
Bit errors are accumulated only when the monitor is in synchronized state. To enter the
synchronize state, the monitor must have synchronized to the incoming PRBS stream and
received 4 consecutive bytes without errors. Once synchronized, the monitor falls out of
synchronization when forced to by programming high the RESYNC register bit, or once it detects
3 consecutive PRBS byte errors. When out of synchronization, detected errors are not
accumulated. However, the 3 errors which cause the PRGM to lose synchronization may in fact
be counted as 3, 4, or 5 errors.
14.22.6 B1/E1 Overwrite and Detection
The B1 and E1 bytes can be used by the PRGM to perform point-to-point connection verification.
One PRGM on one end of a cross-connect can set its B1/E1 bytes to a known value. At the
opposite end of the cross-connect, the receiver’s PRGM can be set up to expect that same B1/E1
value. An error interrupt can be generated if the values do not match.
The monitor is set-up for B1/E1 comparison by setting the B1E1_ENA bit in the PRGM Indirect
Register 0H: Monitor Timeslot Configuration page for each timeslot . The expected value of B1
and E1 is set with the B1[7:0] bits in the The generator is set up to transmit user-defined B1/E1
values by setting the B1E1_ENA bit in PRGM Indirect Register 8H: Generator Timeslot
Configuration Page for each timeslot. The desired B1/E1 value is set using the B1[7:0] bits in the
PRGM Indirect Register BH: Generator B1/E1 Value Page. The E1 values are the complement of
the B1 values.
PRGM Indirect Register 3H: Monitor B1/E1 Value Page (E1[7:0] bits are the inverse of the
B1[7:0] bits). The actual received B1 and E1 values are given in the PRGM Indirect Register 5H:
Monitor Received B1/E1 Bytes Page. If a B1/E1 matching error interrupt is generated by the
PRGM, the B1/E1 values in this register should be compared to the B1[7:0] value in PRGM
Indirect Register 3H to see if they match or not.