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TMXF28155 Super Mapper
155/51 Mbits/s SONET/SDH x28/x21 DS1/E1
Preliminary Data Sheet, Rev. 1
October 2000
340
Lucent Technologies Inc.
M13/M23 Mux/Demux Block Functional Description
(continued)
M13/M23 Demultiplexer
DS3 LOC and LOS
SMPR_RDS3CLK
is monitored for loss of clock, which is reported through bit M13_RDS3_LOC (Table 226). The
user can configure which edge of
SMPR_RDS3CLK
retimes the data (M13_RDS3_EDGE = 1 (Table 288) selects
the rising edge; M13_RDS3_EDGE = 0 selects the falling edge).
The receive DS3 signal is also checked for loss of signal (LOS), which is reported through bit M13_RDS3_LOS
(Table 226). An LOS defect, according to T1.231, is the occurrence of 175 ±75 contiguous pulse positions with no
pulses of either positive or negative polarity at the DS3 input. An LOS defect is terminated upon detecting an aver-
age pulse density of at least 33% over a period of 175 ±75 contiguous pulse positions starting with the receipt of a
pulse. An LOS defect shall not be terminated if, at the end of the pulse-position interval, any subintervals of 100
pulse positions containing no pulses of either polarity were observed (T1.231).
B3ZS Decoder.
The receive DS3 device input can either be in the form of unipolar clock and data
(
SMPR_RDS3CLK
and
SMPR_RDS3POS_DATA
when M13_BIPOLAR = 0 (Table 261)) or unipolar clock, positive
data, and negative data (
SMPR_RDS3CLK
,
SMPR_RDS3POS_DATA
, and
SMPR_RDS3NEG_BPV
when
M13_BIPOLAR = 1 and M13_BPV_IN = 0 (Table 260)) or unipolar clock, data, and bipolar violation indication
(
SMPR_RDS3CLK
,
SMPR_RDS3POS_DATA
, and
SMPR_RDS3NEG_BPV
when M13_BIPOLAR = 1 and
M13_BPV_IN = 1). When M13_BIPOLAR = 0, the received DS3 data and clock are passed directly to the M23
demultiplexer. When M13_BIPOLAR = 1 and M13_BPV_IN = 1, the received DS3 data and clock are passed to the
M23 demultiplexer while the bipolar violation indication is forwarded to the internal BPV counter for performance
monitoring. When M13_BIPOLAR = 1 and M13_BPV_IN = 0, the received
SMPR_RDS3POS_DATA
and
SMPR_RDS3NEG_BPV
data inputs are first B3ZS decoded.
The B3ZS decoder block performs decoding as follows. For each clock period that both
SMPR_RDS3POS_DATA
and
SMPR_RDS3NEG_BPV
are 0 (no pulse), the decoder outputs a 0. For each clock period that either
SMPR_RDS3POS_DATA
or
SMPR_RDS3NEG_BPV
is 1 (pulse), the decoder determines whether or not the pulse
is part of a zero substitution (ZS) sequence. A ZS sequence is [00V] or [B0V], where B is a pulse on either the pos-
itive or negative input that is opposite in polarity to the last non-zero input, and V is a pulse that is the same polarity
as the last non-zero input.
If the received pulse is not part of a ZS sequence, the decoder outputs a 1. Otherwise, the decoder outputs three
consecutive zeros in place of the received ZS sequence.
The B3ZS decoder also checks for bipolar coding violations. Bipolar coding violations are defined as received V-
pulses that are not opposite in polarity to the last V-pulse or are not immediately preceded by a 0, or received 0s
that are immediately preceded by two other 0s.
The M13 contains a counter that increments on each occurrence of a received bipolar coding violation (BPV). It
also monitors the occurrence of excessive zeros (EXZ) which is defined as any zero string length equal to or
greater than 3 (T1.231). These are part of the performance monitoring counters that can be sampled and simulta-
neously reset (see DS3 Performance Monitors on page 344). Their last sampled values are available in registers
M13_BPV_CNT_R[1—3] (Table 296) and M13_EXZ_CNT_R[1—3] (Table 297).
DS3 T-to-R Loopback
The M13 can be configured to loopback the internal transmit DS3 from the output of the M23 mux
(M13_LOOP_T_TO_R = 1 (Table 260)) or accept the received DS3 signal after B3ZS decoding
(M13_LOOP_T_TO_R = 0) and send it into the M23 demux block.