The DS21FT40 MCM offers a high density packaging arrangement for the DS21Q44 E1 Enhanced Quad Framer. Three DS21Q44 silicon die are packaged in a Multi-Chip Module (MCM) with the electrical connections as shown in Figure 1-1. The DS21FT40 is closely related to the DS21FT44. Most of the functions of the DS21FT44 are available on the DS21FT40. The differences are listed in Table 1-1. Table 2-1 lists all of the signals on the MCM. The DS21Q44 E1 Framer is an enhanced version of the DS21Q43 Quad E1 Framer. Each DS21Q44 die contains four framers that are configured and read through a common microprocessor-compatible parallel port. Each framer consists of a receive framer, receive elastic store, transmit formatter and transmit elastic store. All four framers in the DS21Q44 are totally independent, they do not share a common framing synchronizer. Also, the transmit and receive sides of each framer are totally independent. The 1 of 87