Abstract: Tech Brief 7 provides the requirements for multiplexing four PCM streams into one 8MHz system backplane using the Dallas Semiconductor/Maxim DS2152 and DS2154 T1/E1 single chip tranceivers (SCTs). The DS2155, DS26528, DS26524, DS26522, DS26521, DS26519 and DS26518 all contain IBO functionality without external circuitry and are recommended for new designs.

The DS2152 and DS2154 PCM signals can interface to an 8 MHz system backplane. Typically this application is used to mulitplex four 2.048 MHz PCM streams onto a single 8 MHz PCM stream. To accomplish this, the elastic stores are enabled and placed in the 2.048 MHz System Clock mode. Figure 1 describes a timing scheme in which a single RSYNC is generated for all four framers. Each framer in turn is driven with an 8.192 MHz clock burst of 8 cycles. Each clock burst causes the elastic store to output 1 DS0. This results in a "Byte Interleaved" 8.192 MHz PCM stream as shown in Figure 2.


Figure 1.


Figure 2.