MULTI-CHIP MODULE (MCM) DESCRIPTION
The Four x Four and Four x Three MCMs offer a high density packaging arrangement for the DS21Q44 E1 Enhanced Quad Framer. Either three (DS21FT44) or four (DS21FF44) silicon die of these devices is packaged in a Multi-Chip Module (MCM) with the electrical connections as shown in Figure 1-1. All of the functions available on the DS21Q44 are also available in the MCM packaged version.
However, in order to minimize package size, some signals have been deleted or combined. These differences are detailed in Table 1-1. In the Four x Three (FT) version, the fourth quad framer is not populated and hence all of the signals to and from this fourth framer are absent and should be treated as No Connects (NC). Table 2-1 lists all of the signals on the MCM and it also lists the absent signals for the Four x Three.
The availability of both a twelve and a sixteen-channel version allow the maximum framer density with the lowest cost.

FEATURES
• Sixteen (16) or twelve (12) completely independent E1 Framers in one small 27mm x 27mm Package
• Each Multi-Chip Module (MCM) contains either four (FF) or three (FT) DS21Q44 die
• Each quad framer can be concatenated into a single 8.192MHz Backplane Data Stream
• IEEE 1149.1 JTAG-Boundary Scan Architecture
• DS21FF44 and DS21FT44 are pin compatible with DS21FF42 and DS21FT42, respectively to allow the same footprint to support T1 and E1 applications
• 300–pin MCM BGA 1.27 mm pitch package (27mm X 27mm)
• Low power 3.3V CMOS with 5V tolerant input & outputs