DESCRIPTION
The DS21Q44 E1 is an enhanced version of the DS21Q43 quad E1 framer. The DS21Q44 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.

FEATURES
■ Four E1 (CEPT or PCM-30)/ISDN-PRI framing transceivers
■ All four framers are fully independent; transmit and receive sections of each framer are fully independent
■ Frames to FAS, CAS, CCS, and CRC4 formats
■ Each of the four framers contain dual twoframe elastic store slip buffers that can connect to asynchronous backplanes up to 8.192MHz
■ 8-bit parallel control port that can be used directly on either multiplexed or nonmultiplexed buses (Intel or Motorola)
■ Easy access to Si and Sa bits
■ Extracts and inserts CAS signaling
■ Large counters for bipolar and code violations, CRC4 code word errors, FAS word errors, and E-bits
■ Programmable output clocks for Fractional E1, per channel loopback, H0 and H12 applications
■ Integral HDLC controller with 64-byte buffers configurable for Sa bits or DS0 operation
■ Detects and generates AIS, remote alarm, and remote multiframe alarms
■ Pin compatible with DS21Q42 enhanced quad T1 framer
■ 3.3V supply with 5V tolerant I/O; low-power CMOS
■ Available in 128-pin TQFP package
■ IEEE 1149.1 support