Analog Devices Inc./Maxim Integrated DS31256+

Overview

DS31256+ from Maxim Integrated is a 256-channel, high-throughput HDLC controller IC designed for telecom line interface cards and multichannel T1/E1/T3 access equipment. It delivers up to 132Mbps full-duplex throughput, supports 60 T1 or 64 E1 data streams, integrates 16 physical ports with independent channelized/unchannelized configuration, and features three 52Mbps fast HDLC engines on Ports 0–2 - deployed in DSLAMs, frame-relay access concentrators, and SONET/SDH EOC termination systems.

For engineers reviewing the DS31256+ datasheet, DS31256+ pinout, DS31256+ application, or DS31256+ equivalent, key selection criteria include per-port HDLC engine speed grading (52Mbps vs. 10Mbps), PCI v2.1 interface compliance, integrated BERT assignment flexibility, 16kB dual-direction FIFO depth, and 256-pin PBGA package thermal and routing constraints.

Technical Context

The DS31256+ implements a layered architecture with dedicated Layer 1 transceivers per port, 16 standard HDLC engines (each supporting ≤10Mbps unchannelized or ≤8.192Mbps channelized operation), and three accelerated HDLC engines (Ports 0–2, up to 52Mbps). All HDLC engines support transparent mode, per-channel DS0 loopbacks, and V.54 loopback code detection.

It integrates scatter/gather DMA with time-stamped receive packets, transmit priority queuing, and dual 16kB FIFOs - coupled with a 33MHz 32-bit PCI bus interface and optional local bus for bridging or direct host access. The device supports both Intel- and Motorola-style bus signaling and IEEE 1149.1 JTAG for boundary scan.

Key Specifications

Pinout & Package

DS31256+ is housed in a 256-ball plastic BGA (PBGA) package measuring 27mm × 27mm, optimized for telecom board layouts with thermal vias and signal integrity requirements for high-speed serial interfaces.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar HDLC controller applications.

Compared with DS3134 and PM5352, the DS31256+ uniquely balances ultra-high HDLC channel density, selective high-speed ports, and embedded test capability - making it optimal for scalable, service-aware access equipment where PHY independence and diagnostic agility are critical.

Availability

DS31256+ is available at Aetrix Electronics and suitable for DSLAM line cards, frame-relay access concentrators, and T3/E3 router interfaces requiring stable component supply, long-lifecycle support, and RoHS-compliant packaging.

Supply support for DS31256+ 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) is a semiconductor company specializing in precision analog, mixed-signal, and high-reliability ICs for communications, industrial, and computing infrastructure.

The DS31256+ belongs to Maxim's Envoy family of high-density telecom controllers, engineered specifically for carrier-grade T1/E1/T3 access multiplexing and multilink protocol termination in space-constrained line cards.

FAQ

What is the maximum number of T1 data streams supported by the DS31256+?

The DS31256+ supports up to 60 T1 data streams (1.544Mbps each) in channelized mode. This capacity is achieved through its 16 configurable physical ports - each capable of handling one, two, or four T1 lines - and is confirmed in the General Description and Applications sections of the official datasheet. The DS31256+ achieves this density without external channel bonding logic due to its 256 independent HDLC engines.

Does the DS31256+ include an integrated bit error-rate tester (BERT)?

Yes, the DS31256+ includes an on-board BERT with automatic error insertion capability. As stated in the Features list and Section 6.5 of the datasheet, this BERT function can be assigned to any individual HDLC channel or to an entire port - enabling targeted link diagnostics without external test equipment. This capability is a distinguishing feature of the DS31256+ not present in earlier variants like the DS3134.

What package type and dimensions does the DS31256+ use?

The DS31256+ uses a 256-pin plastic BGA (PBGA) package measuring 27mm × 27mm, as specified in the Ordering Information and Package Information sections (page 177). The "+" suffix denotes lead-free/RoHS-compliant construction. This package is thermally optimized for telecom applications with natural convection cooling at 3.0W power dissipation, per Figure 16-1.

How many HDLC engines operate at 52Mbps on the DS31256+?

Exactly three HDLC engines on the DS31256+ operate at up to 52Mbps - those assigned to Ports 0, 1, and 2. This is explicitly documented in the General Description ("three fast HDLC engines that only reside on Ports 0, 1, and 2") and reinforced in the Features list. The remaining 13 ports support up to 10Mbps in unchannelized mode or 8.192Mbps in channelized mode.

Is the DS31256+ compatible with PCI version 2.1?

Yes, the DS31256+ implements a 33MHz, 32-bit PCI interface compliant with PCI Local Bus Specification Revision 2.1, as stated in the Features list and Section 10. The device supports all required PCI transaction types including memory-mapped I/O, configuration space access, and bus mastering via DMA - ensuring interoperability with standard PCI host bridges in telecom chassis.