Analog Devices Inc./Maxim Integrated DS21Q43AT+

Overview

DS21Q43AT+ from Maxim Integrated (now part of Analog Devices) is a quad E1 framing transceiver IC designed for telecom line interface cards and ISDN-PRI access equipment. It integrates four fully independent E1 framers, supports FAS/CAS/CCS/CRC4 framing formats, delivers 2.048 MHz transmit/receive clocks per channel, and operates at 5 V with industrial temperature range (–40°C to +85°C).

For engineers reviewing the DS21Q43AT+ datasheet, DS21Q43AT+ pinout, DS21Q43AT+ application, or DS21Q43AT+ equivalent, this device serves as a space-optimized, pin-compatible upgrade path from DS21Q41B (Quad T1) in E1-centric carrier-grade infrastructure requiring per-framer elastic stores, CAS signaling extraction/insertion, and programmable output clocks for Fractional E1/H0/H12.

Technical Context

The DS21Q43AT+ implements four autonomous E1 framers-each with dual two-frame elastic stores enabling asynchronous/synchronous backplane interfacing up to 8.192 MHz-and shares a single 8-bit parallel control port configurable for multiplexed or non-multiplexed buses. All framers comply with ITU-T G.704, G.706, G.962, I.431 and ETSI 300 011/233 standards.

Each framer provides independent transmit/receive paths with dedicated TCLK/RCLK (2.048 MHz), TSYSCLK/RSYSCLK (1.544/2.048 MHz), and full support for bipolar violation monitoring, CRC4 error detection, FAS word error counting, AIS/remote alarm generation, and per-channel loopback from RSER to TSER.

Key Specifications

Pinout & Package

DS21Q43AT+ is housed in a 128-pin Thin Quad Flat Package (TQFP) with 0.4 mm lead pitch and 14 mm × 14 mm body size, optimized for high-density telecom PCB layouts and thermal performance in line card applications.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar E1 framing applications.

Compared with DS21Q43ATN, the DS21Q43AT+ offers identical electrical and functional behavior but lacks extended temperature certification-making it suitable for commercial indoor telecom gear. Unlike DS21Q41B, it delivers native E1 compliance including G.704 framing, CRC4, and CAS handling, eliminating protocol translation overhead in E1-centric networks.

Availability

DS21Q43AT+ is available at Aetrix Electronics and suitable for E1 line cards, ISDN-PRI gateways, fractional E1 multiplexers, and H0/H12 service termination equipment requiring stable component supply and long-term industrial-grade availability.

Supply support for DS21Q43AT+ includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Analog Devices (via acquisition of Maxim Integrated) designs high-performance analog, mixed-signal, and RF ICs for precision signal processing and connectivity in demanding industrial and communications systems.

The DS21Q43AT+ belongs to Maxim's legacy telecom timing and framing product line, engineered specifically for E1 line interface applications in carrier-class access and transport equipment where reliability, standards compliance, and integration density are critical.

FAQ

What is the primary function of the DS21Q43AT+ in an E1 system?

The DS21Q43AT+ functions as a quad E1 framing transceiver, performing frame alignment (FAS), cyclic redundancy check (CRC4), channel-associated signaling (CAS), and elastic store buffering for four independent 2.048 Mbps E1 links. It handles both transmit and receive paths per framer, supports multiple framing formats (FAS/CAS/CCS/CRC4), and interfaces directly to HDB3 line drivers and backplane controllers. Its design enables compact, high-reliability E1 line cards without external glue logic.

Does the DS21Q43AT+ support both CAS and CCS signaling modes?

Yes, the DS21Q43AT+ supports both Channel Associated Signaling (CAS) and Common Channel Signaling (CCS) modes. The RSM bit (CCR1.3) selects between them: RSM = 0 configures CAS (timeslot 16), while RSM = 1 enables CCS (timeslot 16 used for signaling channel). In CAS mode, the device extracts and inserts Sa/Si bits; in CCS mode, it processes structured signaling frames aligned to multiframe boundaries per ITU-T I.431.

How does the elastic store feature operate in the DS21Q43AT+?

The DS21Q43AT+ includes dual two-frame elastic stores per framer-separately configurable for transmit (RESE=1 in RCR2) and receive (enabled via TCR2.1/RCR2.1) paths. When enabled, these stores absorb timing differences between line-rate (2.048 MHz) and backplane clocks (up to 8.192 MHz), allowing synchronous/asynchronous interface bridging. TSYSCLK/RSYSCLK (1.544/2.048 MHz) drives the store, and TFSYNC/RFSYNC provides frame boundary alignment. Elastic store must be explicitly enabled; otherwise, data flows transparently.

Can the DS21Q43AT+ generate alarms such as AIS or remote alarm automatically?

Yes, the DS21Q43AT+ provides hardware-based automatic alarm generation. AAIS bit (CCR2.5) enables automatic AIS insertion upon loss of frame synchronization, and ARA bit (CCR2.4) enables automatic remote alarm generation when frame alignment is lost. These features operate independently per framer and require no host processor intervention. Alarm status is also reported via RLOS/LOTC outputs and interrupt flag (INT), with configurable polarity and masking via the Interrupt Mask register.

What is the role of the FS0 and FS1 pins on the DS21Q43AT+?

The FS0 and FS1 pins on the DS21Q43AT+ serve as framer-select inputs that determine which of the four internal framers (#0–#3) is accessed via the shared 8-bit parallel control port. Their binary combination (00, 01, 10, 11) maps directly to framer number per Table 1-5. This architecture allows software written for the single-framer DS2143 to be reused with minimal modification-only the framer-select bits need toggling between register accesses to different framers.