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. *The JTAG function on the DS21455/DS21458 is a single controller for all four transceivers, unlike the DS21Q55, which has a JTAG controller-per-transceiver architecture. Applications * Channel Banks * Channel Service Units (CSUs) * Data Service Units (DSUs) * Muxes * Routers * Switches * T1/E1 Test Equipment * Complete T1 (DS1)/ISDN-PRI/J1 Transceiver Functionality * Complete E1 (CEPT) PCM-30/ISDN-PRI 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 Receive- and 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