GENERAL DESCRIPTION
The DS21455 and DS21458 are quad monolithic devices featuring independent transceivers that can be software configured for T1, E1, or J1 operation. Each is composed of a line interface unit (LIU), framer, HDLC controllers, and a TDM backplane interface, and is controlled via an 8-bit parallel port configured for Intel or Motorola bus operations. The DS21455* is a direct replacement for the older DS21Q55 quad MCM device. The DS21458, in a smaller package (17mm CSBGA) and featuring an improved controller interface, is software compatible with the older DS21Q55.

FEATURES
Four Independent Transceivers, Each Having the Following Features:
■ Complete T1 (DS1)/ISDN-PRI/J1 Transceiver Functionality
■ Complete E1 (CEPT) PCM-30/ISDNPRI Transceiver Functionality
■ Short- and Long-Haul Line Interface for Clock/Data Recovery and Waveshaping
■ CMI Coder/Decoder
■ Crystal-Less Jitter Attenuator
■ Fully Independent Transmit and Receive Functionality
■ Dual HDLC Controllers
■ On-Chip Programmable BERT Generator and Detector
■ Internal Software-Selectable Receiveand Transmit-Side Termination Resistors for 75Ω/100Ω/120Ω T1 and E1 Interfaces
■ Dual Two-Frame Elastic-Store Slip Buffers that can Connect to Asynchronous Backplanes Up to 16.384MHz
■ 16.384MHz, 8.192MHz, 4.096MHz, or 2.048MHz Clock Output Synthesized to Recovered Network Clock
■ Programmable Output Clocks for Fractional T1, E1, H0, and H12 Applications
■ Interleaving PCM Bus Operation
■ 8-Bit Parallel Control Port, Multiplexed or Nonmultiplexed, Intel or Motorola
■ IEEE 1149.1 JTAG-Boundary Scan
■ 3.3V Supply with 5V Tolerant Inputs and Outputs
■ DS21455 Directly Replaces DS21Q55
■ Signaling System 7 (SS7) Support
■ RAI-CI, AIS-CI Support