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Analog Devices Inc./Maxim Integrated DS21Q42T
- Part No.:
- DS21Q42T
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Category:
- Telecom
- Package:
- 128-LQFP
- Datasheet:
-
DS21Q42T.pdf
- Description:
- IC TELECOM INTERFACE 128LQFP
- Quantity:
- Payment:
- Shipping:
Inventory:1,601
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Product details
Overview
DS21Q42T from Maxim Integrated is a quad T1 framer IC designed for telecom line interface units and channelized T1 access equipment. It integrates four fully independent T1 framers supporting D4, ESF, and SLC-96 framing formats; provides dual two-frame elastic stores per framer for asynchronous backplane interfacing up to 8.192 MHz; features an 8-bit parallel control port compatible with Intel/Motorola buses; and operates from a 3.3V supply with 5V-tolerant I/O.
For engineers reviewing the DS21Q42T datasheet, DS21Q42T pinout, DS21Q42T application, or DS21Q42T equivalent, this page delivers verified functional architecture, confirmed T1 compliance (ANSI T1.403-1995, ITU G.704/G.706), elastic store timing behavior, HDLC controller configuration for FDL/DS0, and precise pin-level circuit roles - all essential for carrier-grade T1 line card design and migration from DS21Q41B.
Technical Context
The DS21Q42T implements four isolated T1 receive and transmit paths, each with dedicated framing logic, elastic store buffers, and signaling processing - no shared synchronizer or clock domain. Each framer independently supports D4 superframe (12-frame) and ESF extended superframe (24-frame) structures, extracts/inserts robbed-bit signaling, and detects/generates AIS (blue) and RAI (yellow) alarms per ANSI/ITU standards.
Its dual elastic stores per framer operate at up to 8.192 MHz burst rates, enabling phase/frequency alignment between recovered T1 data (1.544 MHz) and asynchronous backplane clocks. The integrated HDLC controller provides 64-byte TX/RX buffers configurable for Facility Data Link (FDL) or DS0 channel access, with hardware-based signaling re-insertion and per-channel loopback capability.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Framing Standards | ANSI T1.403-1995, T1.231-1993; ITU G.704/G.706; AT&T TR62411/54016 - ensures interoperability in North American and international T1 networks |
| Number of Framers | Four independent T1 framers - enables simultaneous handling of four T1 lines without resource contention or cross-framer dependencies |
| Elastic Store Clock Rate | Up to 8.192 MHz burst rate - absorbs jitter and frequency offset between T1 line clock and backplane system clock |
| Control Interface | 8-bit parallel bus with Intel/Motorola timing - direct connection to microprocessor without glue logic or address decoding complexity |
| Supply & I/O | 3.3V core supply with 5V-tolerant I/O - simplifies mixed-voltage board design and interfaces directly with legacy 5V peripherals |
| HDLC Buffer Size | 64-byte TX/RX buffers - supports full FDL message exchange and DS0 data encapsulation without external FIFOs |
| Alarm Detection | RCL, RLOS, RRA, RAIS, AIS-CI - enables real-time fault isolation and automated network management response |
Pinout & Package
DS21Q42T is housed in a 128-pin Thin Quad Flat Package (TQFP) with 0.4 mm pitch, optimized for high-density telecom PCB layouts and thermal dissipation in line card applications.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| TPOS0–TPOS3 | Transmit positive bipolar output | NRZ-encoded T1 data outputs (rising-edge synchronized to TCLK); support B8ZS line coding for EIA-485 compliance |
| RPOS0–RPOS3 | Receive positive bipolar input | Differential T1 line receiver inputs (with RNEGn); tolerate ±10V common-mode range per ANSI T1.403 |
| TSYSCLK0–TSYSCLK3 | Transmit system clock input | Enables elastic store operation; accepts 1.544/2.048 MHz or burst clocks up to 8.192 MHz for backplane synchronization |
| RSYSCLK0–RSYSCLK3 | Receive system clock input | Drives receive-side elastic store; allows phase alignment of recovered T1 data to asynchronous backplane clock domains |
| INT* | Global alarm interrupt output | Active-low open-drain signal asserting on any framer's RLOS, AIS, or RAIS state change - reduces polling overhead in host CPU |
| FS0/FS1 | Framer select address bits | Selects one of four framers (0–3) for register access via shared parallel port - eliminates need for four separate control interfaces |
Key Features
| Feature | Design Value |
|---|---|
| Quad independent T1 framers | Eliminates inter-framer timing coupling; enables true concurrent T1 line monitoring and conditioning across four physical ports |
| Dual two-frame elastic stores per framer | Supports seamless bridging between T1 line rate (1.544 MHz) and variable-rate backplanes (up to 8.192 MHz), critical for packet-over-T1 gateways |
| Programmable fractional T1 output clocks | Enables precise clock synthesis for subrate services (e.g., 384 kbps, 768 kbps) without external PLLs or dividers |
| Integral HDLC controller with FDL/DS0 mode | Offloads protocol processing from host MCU; handles facility data link messaging and DS0 channel data framing in hardware |
| IEEE 1149.1 JTAG boundary scan | Enables in-circuit test and debug of high-pin-count TQFP package without bed-of-nails fixtures - reduces manufacturing test cost |
Applications
| Channelized T1 Access Multiplexer | ISDN PRI Line Card |
|---|---|
Use Scenario: Aggregating 96 DS0 channels from four T1 lines into a single ATM or IP backplane. IC Role / Device Role / Timing Role: DS21Q42T acts as the physical layer framer, extracting signaling, performing frame alignment, and buffering data for backplane transfer via elastic stores. Use Value: Dual elastic stores per framer absorb clock domain mismatches between T1 lines and 8.192 MHz backplane, eliminating bit slips and ensuring error-free multiplexing. | Use Scenario: Providing 23 B-channels + 1 D-channel ISDN PRI service in enterprise PBX or media gateway. IC Role / Device Role / Timing Role: DS21Q42T frames incoming T1 signals, processes D-channel HDLC messages, and manages robbed-bit B-channel signaling. Use Value: Integrated HDLC controller with 64-byte buffers handles full D-channel protocol stack (Q.921/Q.931) in hardware, reducing host processor load by >40% vs. software-only implementations. |
| T1 Network Monitoring Probe | Legacy T1-to-Ethernet Bridge |
Use Scenario: Real-time analysis of T1 line health, including BPV, CV, CRC6, and framing errors across four circuits. IC Role / Device Role / Timing Role: DS21Q42T serves as the front-end framer, detecting RLOS, AIS, RAIS, and calculating standardized error counters per ANSI T1.403. Use Value: Large on-chip error counters (BPV, CV, CRC6, framing bit errors) enable deterministic, zero-latency line diagnostics without host intervention. | Use Scenario: Converting T1 data streams to Ethernet packets for transport over IP infrastructure. IC Role / Device Role / Timing Role: DS21Q42T recovers T1 framing, extracts DS0 channels, and presents time-aligned PCM data to an Ethernet MAC controller via parallel bus. Use Value: 8-bit parallel port with framer-select addressing allows direct connection to FPGA-based packet processors, minimizing latency and external logic. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar quad T1 framer applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| DS21Q41B | Lacks HDLC controller, fractional T1 clock synthesis, and IEEE 1149.1 support; no per-channel code insertion or signaling freezing | Not suitable for FDL-based OAM or bursty backplane sync; requires external HDLC offload | Select DS21Q42T when FDL protocol handling, JTAG testability, or enhanced signaling features are required |
| DS21Q44 | E1-focused (2.048 MHz), supports G.704/G.706 E1 framing only; pin-compatible but not functionally identical for T1 use | Designed for European/E1 infrastructure; lacks T1-specific features like D4 framing and robbed-bit signaling extraction | Choose DS21Q42T for North American T1 deployments; DS21Q44 only where E1 compliance is mandatory |
Compared with DS21Q41B, DS21Q42T adds hardware HDLC, JTAG, and elastic store enhancements - enabling lower-system-cost T1 line cards with reduced MCU overhead. Against DS21Q44, DS21Q42T delivers native T1 feature depth (D4/ESF, robbed-bit, AIS/RAI) essential for ANSI-compliant deployments, while maintaining pin compatibility for drop-in upgrades in existing DS21Q44 footprints configured for T1.
Availability
DS21Q42T is available at Aetrix Electronics and suitable for channelized T1 access multiplexers, ISDN PRI line cards, T1 network monitoring probes, and legacy T1-to-Ethernet bridges requiring stable component supply and long-term industrial temperature support (0°C to +70°C).
Supply support for DS21Q42T 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
Maxim Integrated (now part of Analog Devices) designs precision analog, mixed-signal, and high-reliability semiconductor solutions for communications, industrial, and automotive markets.
The DS21Q42T belongs to Maxim's telecom line interface product line, engineered specifically for carrier-class T1/E1 framer applications demanding ANSI/ITU compliance, low-power CMOS operation, and robust signal integrity in dense line card environments.
FAQ
What is the primary function of the DS21Q42T in a T1 line card?
The DS21Q42T serves as a quad T1 framer IC that performs physical layer framing, synchronization, and signaling processing for four independent T1 lines. It locates D4 or ESF multiframe boundaries, extracts and inserts robbed-bit signaling, detects AIS and RAI alarms, and provides elastic store buffering for backplane interfacing - all within a single 128-pin TQFP package. Its role is foundational to reliable T1 line termination and conditioning.
Does the DS21Q42T support both D4 and ESF framing formats?
Yes, the DS21Q42T natively supports both D4 superframe (12-frame) and ESF extended superframe (24-frame) structures, as confirmed in its functional description and compliance with ANSI T1.403-1995 and ITU G.704. Each of its four framers can be independently configured for either format, enabling flexible deployment across legacy and modern T1 networks.
How does the elastic store in the DS21Q42T handle clock domain crossing?
The DS21Q42T incorporates dual two-frame elastic stores per framer, accepting RSYSCLK/TSYSCLK inputs up to 8.192 MHz. These stores absorb phase and frequency differences between the recovered 1.544 MHz T1 data stream and an asynchronous backplane clock, preventing bit slips during data transfer. The elastic store is independently enabled per framer and supports burst-mode operation for dynamic bandwidth allocation.
Is the DS21Q42T pin-compatible with earlier Maxim quad framers?
Yes, the DS21Q42T is pin-compatible with the DS21Q44 E1 enhanced quad framer, allowing reuse of PCB layouts in multi-standard designs. However, it is not pin-compatible with the DS21Q41B - though software written for DS21Q41B is transferable due to architectural backward compatibility in register mapping and control port behavior.
What signaling protocols does the DS21Q42T support for DS0 channel handling?
The DS21Q42T supports robbed-bit signaling extraction and insertion for DS0 channels in both D4 and ESF formats. It also integrates a full HDLC controller with 64-byte TX/RX buffers configurable for Facility Data Link (FDL) or direct DS0 access, enabling hardware-accelerated Q.921/Q.931 processing for ISDN PRI applications without host CPU involvement.
DS21Q42T Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Series:
- -
- Package/Case:
- 128-LQFP
- Packaging:
- Tube
- Product Status:
- Obsolete
- Function:
- -
- Interface:
- Parallel/Serial
- Number of Circuits:
- 4
- Voltage - Supply:
- 2.97V ~ 3.63V
- Current - Supply:
- 75mA
- Power (Watts):
- -
- Operating Temperature:
- 0°C ~ 70°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 128-LQFP (14x20)
DS21Q42T FAQ
1.How can I place an order for DS21Q42T through Aetrix?
Please submit a Request for Quotation (RFQ) for DS21Q42T on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for DS21Q42T reliable?
The price and inventory of DS21Q42T are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for DS21Q42T is usually 5 days.
3.What payment methods are accepted for DS21Q42T?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for DS21Q42T transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for DS21Q42T?
DS21Q42T orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your DS21Q42T order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for DS21Q42T?
For technical support, including DS21Q42T datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your DS21Q42T requirements.
6.How does Aetrix verify that DS21Q42T is sourced from the original manufacturer or authorized distributors?
All DS21Q42T products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that DS21Q42T meets industry standards.
7.What is the process for return or replacement of DS21Q42T?
All DS21Q42T units undergo pre-shipment inspection (PSI). If there is an issue with DS21Q42T, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The DS21Q42T part is unused and in its original packaging.
Return procedure for DS21Q42T:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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