FEDERAL COMMUNICATIONS COMMISSION RADIO FREQUENCY INTERFERENCE STATEMENT WARNING: This equipment has been certified to comply with the limits for a Class B computing device, pursuant to Subpart J of Part 15 of FCC rules, Only peripherals (computer inputloutput devices, terminals, printers, etc.) certified to comply with the Class B limits may be attached to this computer. Operation with non-certified peripherals is likely to result in interference to radio and TV reception. Notice: As sold by the manufacturer, the IBM Prototype Card does not require certification under the FCC's rules for Class B devices. The user is responsible for any interference to radio or TV reception which may be caused by a user-modified prototype card. CAUTION: This product is equipped with a UGlisted and CSA-certified plug for the user's safety. It is to be used in conjunction with a properly grounded 115 Vac receptacle to avoid electrical shock. Revised Edition (April 1983) Changes are periodically made to the information herein; these changes will be incorporated in new editions of this publication. Products are not stocked at the address below. Requests for copies of this product and for technical information about the system should be made to your authorized IBM Personal Computer dealer. A Reader's Comment Form is provided at the back of this publication. If this form has been removed, address comments to: IBM Corp., Personal Computer, P.O. Box 1328-C, - Boca Raton, Florida 33432. IBM may use or distribute any of the information you supply in any way it believes appropriate without incurring any obligations whatever. O Copyright International Business Machines Corporation, 1981, 1982, 1983 PREFACE - The IBM Personal Computer XT Technical Reference manual describes the hardware design and provides interface information for the IBM Personal Computer XT. This publication also has information about the basic inputloutput system (BIOS) and programming support. The information in this publication is both introductory and for reference, and is intended for hardware and software designers, programmers, engineers, and interested persons who need to understand the design and operation of the computer. You should be familiar with the use of the Personal Computer XT, and you should understand the concepts of computer architecture and programming. This manual has two sections: "Section 1: Hardware" describes each functional part of the system. This section also has specifications for power, timing, and interface. Programming considerations are supported by coding tables, command codes, and registers. "Section 2: ROM BIOS and System Usage" describes the basic inputloutput system and its use. This section also contains the software interrupt listing, a BIOS memory map, descriptions of vectors with special meanings, and a set of low memory maps. In addition, keyboard encoding and usage is discussed. The publication has seven appendixes: Appendix A: ROM BIOS Listings Appendix B: 8088 Assembly Instruction Set Reference . Appendix C: Of Characters, Keystrokes, and Color Appendix I3 Logic Diagrams Appendix E: Specifications Appendix F: Communications Appendix G: Switch Settings A glossary and bibliography are included. iii Prerequisite Publication: Guide to Operations for the IBM Personal Computer XT Part Number 6936810 Suggested Reading: BASIC for the LBM Personal Computer Part Number 6025010 Disk Operating System (DOS) for the IBM Personal Computer Part Number 602406 1 Hardware Maintenance and Service for the IBM Personal Computer XT Part Number 6936809 MACRO Assembler for the IBM Personal Computer Part Number 6024002 Related publications are listed in the bibliography. TABLE OF CONTENTS . Section 1: Hardware IBM Personal Computer XT System Unit . . . . . . . . . . . . . 1-3 IBM Personal Computer Math Coprocesser . . . . . . . . . . . . 1-25 IBM Keyboard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-65 IBM Expansion Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-71 IBM 80 CPS Printers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-81 IBM Printer Adapter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1. 1 07 IBM Monochrome Display and Printer Adapter . . . . . . . . 1-11 3 IBM Monochrome Display . . . . . . . . . . . . . . . . . . . . . . . . . . 1. 1 21 IBM Color/Graphics Display Adapter . . . . . . . . . . . . . . . . 1. 1 23 IBM Color Display . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1. 1 49 IBM 5 4 " Diskette Drive Adapter . . . . . . . . . . . . . . . . . . . 1-15 1 IBM 5-%" Diskette Drive . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1 75 Diskettes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1. 1 77 IBM Fixed Disk Drive Adapter . . . . . . . . . . . . . . . . . . . . . . 1-17 9 IBM lOMB Fixed Disk Drive . . . . . . . . . . . . . . . . . . . . . . . 1. 1 95 IBM Memory Expansion Options .................... 1. 1 97 IBM Game Control Adapter . . . . . . . . . . . . . . . . . . . . . . . . . 1-203 IBM Prototype Card . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-209 IBM Asynchronous Communications Adapter .......... 1-21 5 IBM Binary Synchronous Communications Adapter . . . . . 1-245 IBM Synchronous Data Link Control (SDLC) Communication Adapter .......................... 1-265 IBM Communications Adapter Cable . . . . . . . . . . . . . . . . . 1-295 Section 2:ROM BIOS and System Usage ROM BIOS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2 Keyboard Encoding and Usage . . . . . . . . . . . . . . . . . . . . . . 2-11 Appendix A: ROM BIOS Listings . . . . . . . . . . . . . . A-1 System BIOS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-2 Fixed Disk BIOS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-85 Appendix B: 8088 Assembly Instruction Set Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-1 A.p. p endix C: Of Characters. Keystrokes. and Colors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-1 Appendix D: Logic. Diagrams . . . . . . . . . . . . . . . . . . . D-1 System Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-2 . Type 1 Keyboard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-12 Type 2 Keyboard ................................. D-14 Expansion Board .................................. D-1 5 Extender Card .................................... D-1 6 Receiver Card .................................... D-1 9 Printer . .......................................... D-22 Printer Adapter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-25 Monochrome Display Adapter . . . . . . . . . . . . . . . . . . . . . . D-26 Color/Graphics Monitor Adapter . ................... D-36 Color Display .................................... D-42 Monochrome Display . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-44 5-% Inch Diskette Drive Adapter . ................... D-45 5-% Inch Diskette Drive. T ype 1 . . . . . . . . . . . . . . . . . . . D-49 5-'/4 Inch Diskette Drive. T ype 2 ................... D-52 Fixed Disk Drive Adapter . . . . . . . . . . . . . . . . . . . . . . . . . . D-54 Fixed Disk Drive. T ype 1 . . . . . . . . . . . . . . . . . . . . . . . . . D-60 Fixed Disk Drive. T ype 2 . . . . . . . . . . . . . . . . . . . . . . . . . D-63 32K Memory Expansion Option .. . . . . . . . . . . . . . . . . . . . D-66 64K Memory Expansion Option . . . . . . . . . . . . . . . . . . . . . D-69 641256K Memory Expansion Option . . . . . . . . . . . . . . . . . D-72 Game Control Adapter ............................. D-76 Prototype Card . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-77 Asynchronous Communications Adaptei .............. D-78 Binary Synchronous Communications Adapter . . . . . . . . . D-79 SDLC Communications Adapter . . . . . . . . . . . . . . . . . . . . D-81 Appendix E: Specifications .. . . . . . . . . . . . . . . . . . . . E-1 Appendix F: Communications . . . . . . . . . . . . . . . . . . F- 1 Appendix G: Switch Settings . . . . . . . . . . . . . . . . . . . G-1 Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . H- 1 Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I- 1 i I viii I Notes: