
Preliminary Data Sheet
May 2001
TMXF28155/51 Super Mapper
155/51 Mbits/s SONET/SDH x28/x21 DS1/E1
469
Agere Systems Inc.
20 M13/M23 MUX/DeMUX Block Functional Description
(continued)
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 nonzero input, and V is a pulse that is the same polarity
as the last nonzero 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
zeros that are immediately preceded by two other zeros.
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 472
). Their last sampled values are available in registers
M13_BPV_CNT_R[1
—
3] (
Table 295
) and M13_EXZ_CNT_R[1
—
3] (
Table 296
).
20.11.2 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 259
)) or accept the received DS3 signal after B3ZS decoding
(M13_LOOP_T_TO_R = 0) and send it into the M23 deMUX block.
20.11.3 M23 Demultiplexer
The M23 demultiplexer will take the received DS3 signal and either deMUX it into 7 DS2 data streams or strip off
the overhead bits and send payload out through the NSMI serial interface when M13_NSMI_MODE (
Table 277
) =
1.
The serial data interface, when enabled (M13_NSMI_MODE = 1), generates a clock M13_DNSMI_CLK and an
enable M13_DNSMI_EN for outputting DS3 payload data M13_DNSMI_DATA. A sync pulse M13_DNSMI_SYNC,
in reference to and ahead of the first M bit within a DS3 frame, is also generated. The offset from the sync pulse to
the first M bit is programmable through bits M13_D_SP_OFFSET[7:0] (
Table 262
).
In the case of the received DS3 signal being deMUXed into 7 DS2s, those DS2s can be sent out of the device, or
looped back to the transmit side, or passed to M12 demultiplexers for further breakdown into DS1s/E1s.
DS3 Framer.
After being B3ZS decoded, the incoming DS3 data stream is checked for the presence of unframed
all ones. If the input data is 0 for fewer than 9 out of 8192 clock periods, bit M13_RDS3_ALL1_DET (
Table 225
) will
be set.
The M23 demultiplexer determines if the input signal contains valid DS3 framing. This is done in two stages by first
finding a bit position that matches the frame alignment pattern (F bits), and then locating the multiframe alignment
signal (M bits). After a matching F-bit sequence is found, in-frame is declared (M13_DS3_OOF = 0 (
Table 224
))
when correct M bits are received for three consecutive M frames (T1.231). The maximum average reframe time is
0.5 ms in the presence of a bit error rate of 10
–
3
.
Once the deMUX is in-frame, the received frame bits are monitored for out-of-frame. Out-of-frame is declared
(M13_DS3_OOF = 1) when too many errors are received in either the F bits (three errors in 16 bits when
M13_DS3_MODE = 0 (
Table 287
), or at least 1 F-bit error in each of
four
consecutive M-subframes when
M13_DS3_MODE = 1) or the M bits (at least 1 error in each of
three
consecutive M frames) (T1.231). For testing
purposes, the user may also force the framer out-of-frame by setting M13_DS3_FORCE_OOF (
Table 258
) to 1.