Analog Devices Inc./Maxim Integrated DS31256B

Overview

The DS31256B from Maxim Integrated is a 256-channel, high-throughput HDLC controller designed for telecom line interface cards and multichannel T1/E1/T3 termination. It supports up to 60 T1 or 64 E1 data streams, delivers 132Mbps full-duplex throughput, features 16 physical ports with independent channelized/unchannelized configuration, and integrates three 52Mbps fast HDLC engines on Ports 0–2 - deployed in DSLAMs, frame-relay access concentrators, and SONET/SDH ECC termination systems.

For engineers reviewing the DS31256B datasheet, DS31256B pinout, DS31256B application, or DS31256B equivalent, key selection considerations include per-port HDLC engine speed grading (52Mbps vs. 10Mbps), PCI v2.1 interface compliance, 256-pin PBGA package dimensions (27mm × 27mm), BERT assignment flexibility across channels, and Layer 1 timing support for T1/E1/T3 physical layer framing.

Technical Context

The DS31256B implements a hierarchical architecture with dedicated Layer 1 blocks per port, 16 independent HDLC processing engines (13 standard + 3 fast), dual-direction 16kB FIFOs, scatter/gather DMA controllers, and dual-bus connectivity via 33MHz 32-bit PCI and configurable local bus (Intel/Motorola signaling). Its HDLC engines operate at up to 8.192Mbps (channelized) or 10Mbps (unchannelized), while Ports 0–2 support 52Mbps unchannelized operation.

Layer 1 functionality includes V.54 loopback code detection, per-channel DS0 loopbacks in both directions, over-subscription capability at the port level, and transparent mode support. The on-board BERT supports automatic error insertion and can be assigned to any HDLC channel or port - enabling in-system link integrity validation without external test equipment.

Key Specifications

Pinout & Package

The DS31256B is housed in a 256-ball plastic BGA package (27mm × 27mm, 1.27mm pitch), optimized for high-density telecom line card layouts with thermal vias and ground/power plane integration.

Key Features

Applications

Equivalent & Alternatives

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

Compared with DS31256B, DS3134 provides half the channel density and no T3 support but lowers BOM cost for T1/E1-only systems; PM5352 adds SONET framer capability but increases design complexity and cost - DS31256B remains optimal for pure HDLC-intensive, high-density T1/E1/T3 termination where framer logic is handled externally.

Availability

The DS31256B is available at Aetrix Electronics and suitable for DSLAM line cards, frame-relay access concentrators, and T3/E3 gateway modules requiring stable component supply, long-term lifecycle assurance, and RoHS-compliant packaging.

Supply support for DS31256B 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 industrial, communications, and computing markets.

The DS31256B belongs to Maxim's Envoy family of telecom interface controllers, engineered specifically for high-density, multi-protocol TDM-to-packet aggregation in carrier-class access and edge infrastructure.

FAQ

What is the maximum number of T1 data streams supported by the DS31256B?

The DS31256B supports up to 60 T1 data streams. This capacity is achieved through its 16 physical ports, each configurable to handle one, two, or four T1 lines in channelized mode. The DS31256B's architecture allocates HDLC channel resources dynamically across ports, enabling flexible deployment in T1-centric access networks such as business service gateways and remote DSLAMs.

Does the DS31256B support E1 data streams, and if so, how many?

Yes, the DS31256B supports up to 64 E1 data streams. Each of its 16 ports can be independently configured for E1 operation in channelized mode, with scalability matching T1 configurations. The DS31256B maintains full E1 framing compliance (G.704/G.706), including CAS/EAS signaling support and CRC-4 multiframe handling - making it suitable for European and global metro access applications.

What are the key differences between the standard HDLC engines and the three fast HDLC engines in the DS31256B?

The DS31256B includes 13 standard HDLC engines (on Ports 3–15) rated up to 10Mbps unchannelized or 8.192Mbps channelized, and three fast HDLC engines (on Ports 0–2) rated up to 52Mbps unchannelized. The DS31256B uses these fast ports for high-bandwidth T3/E3 termination, while standard ports handle T1/E1 aggregation - enabling mixed-line-rate line cards without performance bottlenecks.

Is the DS31256B compatible with PCI version 2.1, and what are its electrical requirements?

Yes, the DS31256B implements a fully compliant 33MHz, 32-bit PCI v2.1 interface with support for memory-mapped and I/O-mapped transactions. It operates from a 3.3V supply with 5V-tolerant I/O pins - allowing direct connection to legacy 5V PCI slots via level-shifting or to modern 3.3V-only backplanes without external translation. The DS31256B meets all PCI v2.1 timing and electrical specifications per its AC characterization tables.

How does the on-board BERT function in the DS31256B, and can it be assigned to any channel?

The DS31256B integrates a fully programmable bit error-rate tester (BERT) with automatic error insertion capability. It can be assigned to any of the 256 HDLC channels or to any of the 16 physical ports - enabling targeted link validation without reconfiguring external test gear. The DS31256B's BERT supports PRBS patterns (2^15, 2^20, 2^23), error counting, and real-time pass/fail reporting via status registers - accelerating field commissioning and troubleshooting.