TXC-02201

The TXC-02201 has the following features including Multiplexes/demultiplexes three serial STS-1 signals from an STS-3;Byte parallel or nibble parallel STS-3 interface;Scrambling and B1 BIP-8 byte functions enabled with an STS-3 byte intertace;Loss of STS-3 receive detector and loss of STS-1 transmit signal detectors;Provides reference timing for transmit timing:-From higher order multiplexer for STS-3 nibble interface,-From 155 MHz clock for STS-3 byte intertace.

The TXC-02201 SM3 is a CMOS VLSI device that provides the functions needed to multiplex and demultiplex three STS-1 signals to and from an STS-3 signal. The SM3 provides either a byte parallel or nibble parallel interface on the line side. When the byte intertace is selected, the SM3 performs the line signal scrambling/descrambling and the B1 generation and detection functions.On the terminal side, the SM3 provides three serial interfaces for the STS-1 signals. Each of the serial interfaces  can  be directly  connected  to  a  TranSwitch SONET Overhead Terminator (SOT-1),TXC-03001,or to other transport and path overhead terminating circuitry. STS-1 transmit reference timing in the STS-3 byte interface mode is provided by using an external 155  MHz clock.  For an STS-3 nibble intertace, the STS-1 reference timing is provided by the SM3 from the higher order multiplexer circuits.

The order of transmission of the bytes in the frame is row by row, from left to right, starting with row 1 .Thus,the framing pattern formed is F6F6F6282828 Hex. In an STS-3 signal, not all of the STS-1 transport overhead bytes are assigned for use. Table 1 summarizes the transport overhead bytes that are required in each of the STS-1 signals when they are multiplexed into an STS-3 signal. An X in the table indicates that the byte is assigned, while a dash indicates that TXC-02201 is unused. The contents of an unused byte carries the value of zero.The STS-1 C1 byte carries the binary number corresponding to its order of appearance in the STS-3 signal. If the STS-3 signal is converted to an OC-3 signal, all of the bytes in the signal,except the six A1 and A2 framing bytes and three C1 bytes, are scrambled, and a BIP-8 is calculated and inserted into the STS-1 No. 1 B1 byte.