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TMXF28155 Super Mapper
155/51 Mbits/s SONET/SDH x28/x21 DS1/E1
Preliminary Data Sheet, Rev. 1
October 2000
342
Lucent Technologies Inc.
M13/M23 Mux/Demux Block Functional Description
(continued)
M13/M23 Demultiplexer
(continued)
AIS, Idle, and RAI Detection.
Each M-frame, the 4704 information bits are checked for the presence of the AIS
(1010) or idle (1100) pattern. In order to detect these patterns in the presence of a high error rate, AIS
(M13_DS3_AISPAT_DET = 1 (Table 225)) or idle (M13_DS3_IDLEPAT_DET = 1 (Table 225)) pattern detection is
declared if fewer than 5 pattern errors are received in each of 2 consecutive frames. Once AIS or idle is declared,
these bits are not cleared until at least 16 pattern errors are received in each of 2 consecutive frames (T1.231).
In addition to the fixed information bit patterns, AIS and idle signals are transmitted with all C bits set to 0 and both
X bits set to 1. These conditions are monitored by the M13 and reported in bits M13_DS3_CBZ_DET (Table 225)
and M13_DS3_RAI_DET (Table 225).
If every C bit in 3 consecutive DS3 frames is 0, the M13 sets M13_DS3_CBZ_DET to 1. If the three C bits in a sin-
gle M-subframe are all 1, M13_DS3_CBZ_DET is cleared. If both X bits in 2 consecutive frames are received as 0,
the device sets M13_DS3_RAI_DET to 1. Once M13_DS3_RAI_DET is set, it is not cleared until both X bits in 2
consecutive frames are received as 1.
The user may wish to declare AIS or idle based on a combination of some or all of the following bits:
M13_DS3_CBZ_DET, M13_DS3_RAI_DET, and M13_DS3_AISPAT_DET or M13_DS3_IDLEPAT_DET.
C-Bit Processing.
The M13 can be provisioned to operate in either the M23 mode (M13_M23_CBP = 1
(Table 261)) or the C-bit parity mode (M13_M23_CBP = 0). In the M23 mode, the C bits in each M-subframe are
interpreted as stuff indicator bits, and they are checked for loopback requests. If the third C bit differs from the first
and second C bits in the yth M-subframe for 5 successive DS3 frames, M13_DS2_LB_DETy (Table 245) is set to 1.
The M13_DS2_LB_DETy bit is cleared when the third C bit does not differ from the first two C bits in subframe y for
5 successive DS3 frames.
The first C bit of each frame, C1, provides C-bit parity identification. If for 8 consecutive frames it is received as a 1,
the M13 sets M13_DS3_C1_DET (Table 225) to 1. Once M13_DS3_C1_DET bit is set, 3 consecutive frames with
C1 = 0 must be received before it is cleared.
The RCBDATA (pin E15) output provides access to the received C2, C4, C5, C6, and C16 through C21 C bits. The
received data link bits, C13 through C15, are output as a serial stream on RDLDATA pin (H22).
FEAC.
In the C-bit parity mode, the third C bit of each DS3 frame, C3, is monitored for FEAC signals. Active FEAC
signals consist of repeating 16-bit code words of the form 0 x5x4x3x2x1x0 0 11111111, where xi can be a 1 or a 0,
and the bits are received right-to-left. The same code word must be received 4 consecutive times before it is
accepted.
When a code word is accepted, the action taken by the M13 depends on the value of x5x4x3x2x1x0, which may be
an alarm indication, a loopback activation, or a loopback deactivation.
The values of M13_DS1_FEAC_LB_DETx and M13_DS3_FLB_DET bits are not changed if an activate or deacti-
vate control signal is accepted, but the next code word to be accepted is not a channel indication control signal
(010011, 011011, or 100001 through 111100).
Alarm, Status, or Unassigned Signals.
If a FEAC signal is accepted that is not a loopback activate (000111),
deactivate (011100), or channel indication (010011, 011011, or 100001 through 111100) signal, the M13 will set
bits M13_RFEAC_CODE[5:0] = x5x4x3x2x1x0 and M13_RFEAC_ALM_INT (Table 218) to 1.