
DS31256 256-Channel, High-Throughput HDLC Controller
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1. MAIN FEATUERS
Layer 1
Can simultaneously support up to 60 T1 or 64 E1
data streams, or two T3 data streams
16 independent physical ports capable of speeds
up to 10MHz; three ports are also capable of
speeds up to 52MHz
Each port can be independently configured for
either channelized or unchannelized
operation
Each physical channelized port can handle one,
two, or four T1 or E1 data streams
Supports N x 64kbps and N x 56kbps
On-board V.54 loopback detector
On-board BERT generation and detection
Per DS0 channel loopback in both directions
Unchannelized loopbacks in both directions
HDLC
256 independent channels
Up to 132Mbps throughput in both the receive
and transmit directions
Transparent mode
Three fast HDLC controllers capable of
operating up to 52 MHz
Automatic flag detection and generation
Shared opening and closing flag
Interfame fill
Zero stuffing and destuffing
CRC16/32 checking and generation
Abort detection and generation
CRC error and long/short frame error detection
Invert clock
Invert data
FIFO
Large 16kB receive and 16kB transmit buffers
maximize PCI bus efficiency
Small block size of 16 Bytes allows maximum
flexibility
Programmable low and high watermarks
Programmable HDLC channel priority setting
Governing Specifications
The DS31256 fully meets the following specifications:
ANSI (American National Standards Institute) T1.403-1995 Network-to-Customer Installation DS1 Metallic
Interface March 21, 1995
PCI Local Bus Specification V2.1 June 1, 1995
ITU Q.921 March 1993
ISO Standard 3309-1979 Data Communications–HDLC Procedures–Frame Structure
DMA
Efficient scatter-gather DMA minimizes system
memory utilization
Programmable small and large buffer sizes up to
8188 Bytes and algorithm select
Descriptor bursting to conserve PCI bus
bandwidth
Identical receive and transmit descriptors
minimize host processing in store-and-
forward
Automatic channel disabling and enabling on
transmit errors
Receive packets are timestamped
Transmit packet priority setting
PCI Bus
32-bit, 33MHz
Version 2.1 Compliant
Contains extension signals that allow adoption to
custom buses
Can burst up to 256 32-bit words to maximize
bus efficiency
Local Bus
Can be bridged from the PCI bus to simplify
system design, or a configuration bus
Can arbitrate for the bus when in bridge mode
Configurable as 8 or 16 bits wide
Supports a 1MB address space when in bridge
mode
Supports Intel and Motorola bus timing
JTAG Test Access
3.3V low-power CMOS with 5V tolerant I/Os
256-pin plastic BGA package (27mm x 27mm)