Analog Devices ee-106 Application Notes

Engineer To Engineer Note EE-106

Pin 1

Pin 14

Pin 26

Pin1

Outer Shields

Pin 13

Pin 26

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Link Port Open Systems
Interconnect Cable Standard

Last Modified: 11/10/99

Contributed by: Robert Kilgore

Overview

This note describes a cabling standard for
connecting multiple SHARC DSPs located on boards
that are installed in close proximity to each other in
the same system. This standard applies to ADSP­21160 and future SHARC products that use 8-bit
link port data transfers.

Cable Specifications

The standard is based on the Honda 26 pin
connector.

The cable consists of twelve 50 Ohm coax strands
and two 28 AWG stranded wires inside a shield,
which ensures minimum cross talk and emissions.
The outer shield is a mesh conductor enclosed in an
outer shell of nonconductive material.

Users can define the function of the two 28 AWG
stranded wires.

This standard is intended for use with cable of
arbitrary length. But, unless the signals are
buffered at each end, the maximum length of the
cable must not exceed one meter.

Honda 26 Pin Connector

The Honda connector RMCA-26JL-AD consists of
two rows of thirteen pins. Facing the PC board,

they are arranged as shown in Figure 1.

Pin 13

Figure 1. Honda RMCA-26JL-AD connector

At the surface mount pads, pins 14 through 26 are
interleaved between pins 1 through 13 as shown in

Figure 2.

Pin14

Pin2

Figure 2. Connector pin arrangements at the surface
mount pads

Table 1 lists and describes the pin and signal

assignments for the connector on the printed circuit
board.

Pin ADSP-21160 Connection

1 UD1
2 CLOCK
3 ACK
4 D0
5 D1
6 D2
7 D3
8 D4

a

Pin ADSP-21160 Connection

9 D5
10 D6
11 D7
12 No connect
13 No connect
14 CLOCK SHIELD
15 ACK SHIELD
16 D0 SHIELD
17 D1 SHIELD
18 D2 SHIELD
19 D3 SHIELD
20 D4 SHIELD
21 D5 SHIELD
22 D6 SHIELD
23 D7 SHIELD
24 No connect
25 No connect
26 UD2
— Outer shields connect to chassis GND

Required Cable Materials

Table 2 lists and describes the materials needed to

make a link port cable that adheres to this open
systems interconnect standard.

Qty. Mfr. Part # Description

2 Honda RMCA-E26F1S-A Cable connector
2 Honda RMCA-E26L1A Shroud
12 × length Gore DXN2132 50 Ohm coax
2 × length Any 28 AWG wire
Length Any Braided outer shield
Length Any Nonconductive outer

coating

Table 2. Cable manufacturing materials

The male PC board connector is the Honda RMCA­26JL-AD, which provides above-board mounting.

Additional form factors of this PC board connector
that require a cut out to enable the board to accept
the connector are:

Table 1. Connector pin assignments

Signal Usage

The data sheets for ADI’s SHARC DSPs define the
use and behavior of most of the signals listed in

Table 1.

Guide lines for the use of the user-defined signals,
UD1 and UD2, are:

• Since the cable has no provisions to prevent

user-defined outputs shorted to user-defined
outputs, these outputs must have a 50 Ohm
series resistor added to the circuit board.

• User-defined signals must use 3.3V logic

levels and have 5V tolerance.

• User-defined signals are intended for low-

frequency communications, such as reset or
functional synchronization signals.

• To use reset as an input or an output on the

link port cable, use the UD1 connection.
(For a detailed description of a
recommended reset circuit, see

• RMCA-EA26LMY-OM03

• RMCA-EA26LMY-OM06

• RMCA-EA26LMY-OM09

Cable Assembly

The methods of assembly mentioned in this note are
a recommendation only. Reasonable deviations that
do not affect the function of the finished product are
permitted without written approval.

Individual coax strands were chosen instead of a
preassembled cable to enable machine fabrication of
wire ends and cable assembly.

The connector pin out was chosen so designers could
attach an assembly of an inner layer of coax to the
connector—COAX1, COAX3, COAX5, COAX7, and
so on—and later attach the outer layers—COAX2,
COAX4, COAX 6, and so on

• Reset and Synchronization on page 3.)

EE-106 Page 2

Technical Notes on using Analog Devices’ DSP components and development tools

Phone: (800) ANALOG-D, FAX: [phone], EMAIL: [e-mail], FTP: ftp.analog.com, WEB:

www.analog.com/dsp