DS31256

Telecom Overview

The DS31256 Envoy is a 256-channel HDLC controller designed for high-throughput telecommunications applications. It supports up to 60 T1 or 64 E1 data streams, or two T3 data streams across 16 physical ports. Each port can be independently configured for channelized or unchannelized operation, with speeds up to 10Mbps in unchannelized mode and up to 8.192Mbps in channelized mode. Three fast HDLC engines on Ports 0, 1, and 2 support speeds up to 52Mbps. The device features a 33MHz 32-bit PCI interface, large 16kB FIFOs, and efficient scatter/gather DMA.

Telecom Feature Summary

• Supports 256 independent bidirectional HDLC channels with per-channel loopbacks
• Includes onboard bit error-rate tester (BERT) with automatic error insertion capability
• Provides efficient scatter/gather DMA to maximize memory efficiency
• Features receive data packet time-stamping and transmit packet priority setting

Telecom Applications

• Channelized and Clear-Channel T1/E1 and T3/E3 Routers with Multilink PPP Support
• High-Density Frame-Relay Access
• xDSL Access Multiplexers (DSLAMs)
• Triple HSSI
• SONET/SDH EOC/ECC Termination

Telecom Procurement Notes

Verify the specific ordering suffix when purchasing. The standard DS31256 operates within a commercial temperature range of 0°C to +70°C. The DS31256+ variant denotes a lead-free and RoHS-compliant package. Ensure the selected part matches the required environmental specifications for the target application before procurement.

Telecom Selection Notes

Select this component for designs requiring high-density HDLC processing with significant throughput requirements. The device accommodates various T1, E1, and T3 configurations through flexible port settings. Consider the available fast ports for higher speed interfaces if needed. Verify compatibility with existing PCI bus architectures and local bus requirements for system integration.

Telecom Part Context

The DS31256 is part of Analog Devices' (formerly Maxim Integrated) Envoy family of HDLC controllers. It serves as a high-performance solution for managing multiple serial data streams in networking equipment. The device integrates Layer 1 processing, HDLC handling, and DMA capabilities into a single chip, reducing system complexity compared to multi-chip solutions.

Telecom Replacement Considerations

The datasheet notes backward compatibility with the DS3134. Designers migrating from older components should verify register-level differences and timing characteristics to ensure seamless integration without hardware modifications.