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NCR 5385E15386 SCSI
Protocol Controller
User's Guide




Microelectronics Division, Colorado Springs
Copyright @1983, by NCR Corporation
Dayton, Ohio
All Rights Reserved Printed in U. S.A.




This document contains the latest information available at the time of publication. However, NCR
reserves the right to modify the contents of this material at any time. Also, all features, functions and
operations described herein may not be marketed by NCR in all parts of the world. Therefore, before
using this document, consult your NCR representative or NCR office for the information that is
applicable and current.
TABLE OF CONTENTS




SECTION PAGE
1. INTRODUCTION ................................................................3
2. INITIALIZATION ................................................................4
3. INITIATOR ROLE ...............................................................5
3.1 Initiator Role Walkthrough .................................................7
3.2 Notes ...................................................................12
4. TARGET ROLE .................................................................13
4.1 Target Role Walkthrough ................................................. 16
4.2 Notes ...................................................................19
5. INTERRUPT SERVICE ROUTINES (ISR) ..........................................20
5.1 General .................................................................20
5.2 User Disconnected ISR ...................................................21
5.3 User Connected as Target ISR ............................... " ............. 22
5.4 User Connected as Initiator ISR ...........................................24
5.4.1 Bus Service Interrupt .....................................................25
5.5 Interrupt Summary .......................................................26
6. SCSI BUS INTERFACE ..........................................................28
APPENDICES

APPENDIX PAGE
A. NCR 5385 SCSI Protocol Controller Register and Command Summary ................ 34
B. Internal Registers ...............................................................35
C. Initiator/Target Role Flowchart ....................................................36




LIST OF TABLES

TABLE PAGE
5.1 Interrupt Summary ..............................................................27




LIST OF FIGURES

FIGURE PAGE
3.1 Initiator Role Flowchart ............................................................ 5
4.1 Target Role Flowchart. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
5.1 Auxiliary Status Register .......................................................... 20
5.2 Interrupt Register ................................................................ 20
6.1 Suggested Interface to SCSI Differential Transceivers .................................. 29
6.2 NCR 8310 Equivalent Circuit ...................................................... 30
6.3 Single-Ended Interface Using the NCR 8310 Driver/Receiver Chip ....................... 31




2
SECTION 1
GENERAL INFORMATION
The NCR SCSI Protocol Controller is capable of operating as either an Initiator or a Target, and can therefore
be used in host adapter and control unit designs. The purpose of this manual is to assist the user in the design of
these SCSI bus devices.

Sections 2 through 5 discuss the software required to control the device. Sample flowcharts and step-by-step
walk-through's demonstrate the required routines for both the Initiator and Target roles. Additionally, the interrupt
service routines presented in Section 5 cover all possible interrupting conditions for the Connected as Initiator,
Connected as Target and Disconnected states.

Section 6 describes the inteface required between the NCR 5385E/86 and SCSI bus for both Single-Ended and
Differential-Pair operation, and provides sample schematics for each.

This design manual is not an SCSI specification and assumes some prior knowledge of the SCSI proposed stan-
dard. Copies of the proposed standard may be obtained, with a pre-payment of $20, from:

X3 Secretariat, Computer and Business Equipment
Manufacturers Association
311 First Street, NW, Suite 500
Washington, D.C. 20001

Please include a self-addressed mailing label.

1.1 ADDITIONAL DOCUMENTATION
Other documents which may be useful are: