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Preliminary Data Sheet, Rev. 1
October 2000
TMXF28155 Super Mapper
155/51 Mbits/s SONET/SDH x28/x21 DS1/E1
343
Lucent Technologies Inc.
M13/M23 Mux/Demux Block Functional Description
(continued)
M13/M23 Demultiplexer
(continued)
Control Signals.
EAC control signals are defined for activating or deactivating a loopback. If a loopback activate
(000111), deactivate (011100), or channel indication (010011, 011011, or 100001 through 111100) is accepted,
the M13 will set bits M13_RFEAC_CODE[5:0] (Table 253) = x5x4x3x2x1x0 and M13_RFEAC_LB_INT (Table 218)
to 1.
If a loopback activate (000111) followed by the all DS1 channels indication (010011) is accepted, the device sets
all M13_DS1_FEAC_LB_DETx (Table 252) bits. All M13_DS1_FEAC_LB_DETx bits are cleared if a loopback
deactivate (011100) followed by the all DS1 channels indication is accepted.
If a loopback activate (000111) followed by the DS3 indication (011011) is accepted, the device sets the
M13_DS3_FLB_DET (Table 252) bit. The M13_DS3_FLB_DET bit is cleared if a loopback deactivate (011100) fol-
lowed by the DS3 indication is accepted.
Similarly, if the M13 accepts an activate or deactivate control signal followed by a DS1 channel indication (100001
through 111100), it sets or clears the M13_DS1_FEAC_LB_DETx bit, where x is equal to the binary value of
x5x4x3x2x1x0.
Terminal-to-Terminal Path Maintenance Data Link.
C bits 13, 14, and 15 can be used as a 28.2 kbit/s data link.
These bits are available directly at device output pin RDLDATA (H22). The M13 also contains an internal HDLC
receiver for processing the received data link bits.
HDLC Receiver.
The internal HDLC receiver circuitry is composed of a 128-byte FIFO, a CRC-16 frame check
sequence (FCS) error detector, and control circuits.
The HDLC receiver searches for flag bytes (01111110) and processes the bits received between flag bytes as fol-
lows. The receiver removes zeros that immediately follow any sequence of five consecutive ones. Sequences of 8
bits after zero destuffing are grouped into bytes and written into the FIFO.
As bytes are received, the CRC-16 value based on the ITU-T polynomial is calculated. When the closing flag is
received, the receiver checks that the received FCS in the final 2 bytes matches the calculated CRC-16. If
M13_RDL_FCS = 1 (Table 288) and the FCS does not match, M13_RDL_FCS_ERR (Table 254) is set. If
M13_RDL_FCS = 0, M13_RDL_FCS_ERR
is held reset at 0. M13_RDL_FCS bit also determines whether or not
the final 2 bytes of the frame are written into the FIFO. They are written into the FIFO only when M13_RDL_FCS =
0.
The receiver allows frames to be sent back-to-back with the closing flag of one frame shared as the opening flag of
the next frame. If fewer than 3 complete destuffed bytes are received between flag bytes, the receiver ignores the
data and writes nothing into the FIFO.