tmxf28155 ETC-unknow, tmxf28155 Datasheet - Page 464

• Manufacturer Part Number: tmxf28155
• Description: Tmxf28155 Super Mapper 155/51 Mbits/s Sonet/sdh X28/x21 Ds1/e1
• Manufacturer: ETC-unknow

155/51 Mbits/s SONET/SDH x28/x21 DS1/E1
20 M13/M23 MUX/DeMUX Block Functional Description
The parity bits (P bits) are generated as odd rather than the normal even parity if M13_DS3_PINV
set. Both P bits within the first DS3 frame after a 0 to 1 transition of SMPR_BER_INSRT
inverted if M13_DS3_P_BERy
The X bits are set to the inverse of the remote alarm indication (RAI) bit (GR-499) M13_DS3_RAI_SEND
(Table
C-bit transmission is a function of whether the M13 MUX/deMUX is in the M23 mode or the C-bit parity mode.
20.7.4 M23 Mode
Please refer to M13_M23_CBP = 1 in
select blocks. If M13_M23CLK_MODE = 0
state, the selected DS2 must be synchronized to the DS3 frame generation clock. To do this, the M13 contains
7 DS2 FIFOs each with a depth of 8. The fill level of each FIFO determines the need for bit stuffing its DS2 input.
When M13_M23CLK_MODE = 0 and DS2 select blocks are not in the loopback or direct DS2 input state, the
selected DS2s are generated using the DS3 frame generation clock. In this case, a fixed stuffing ratio is used for
the DS2s in order to produce a nominal 6.312 MHz DS2 clock rate.
When M13_M23CLK_MODE = 1, the FIFOs are not used and DS2 stuff request inputs (XC_DS2STFREQ[7—1])
will determine when stuff bits are needed.
The three C bits in each M-subframe of the DS3 frame are stuff indication bits. If the stuff opportunity bit in an M
subframe is filled by a DS2 bit, the first and second C bits in that M-subframe are transmitted as zeros. If the stuff
opportunity bit in an M-subframe is filled with a stuff bit, the first and second C bits in that M-subframe are transmit-
ted as ones.
The third C bit in each M-subframe is normally transmitted with the same value as the first and second C bits. How-
ever, if M13_DS2_LB_REQy = 1
(which indicates a loopback request for DS2 channel y).
20.7.5 C-Bit Parity Mode
Please refer to M13_M23_CBP = 0 in
lowing two circumstances:
In the C-bit parity mode, every DS2 stuffing opportunity is filled with a stuff bit. Because stuffing is not used for syn-
chronization, the selected DS2s cannot come directly from the M13 inputs, and the selected DS2s cannot be
looped back from the M23 demultiplexer. The 21 C bits in each DS3 frame are not required as stuffing indicators.
Their use is described in
464
When M13_M23CLK_MODE = 0 and 28 DS1 or 21 E1 signals are being MUXed into the DS3.
When M13_M23CLK_MODE = 1 and 7 DS2 signals are being MUXed into the DS3.
277).
Table 575 on page
(Table
(Table
277) is set to 1.
Table
Table
281), the third C bit is transmitted as the inverse of the first two C bits
(Table
260.
260.
465.
The information bits in the DS3 frame are drawn from the 7 DS2
The M23 MUX can operate in the C-bit parity mode under the fol-
276) and a select block is in the loopback or direct DS2 input
(continued)
(Table
65) are also
Agere Systems Inc.
(Table
May 2001
276) is