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Reader's Guide ........................................................ " . . . . . . . . . . . .. 3
I. General Background Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . .. 4
A. The Task of an Interface. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... . . . . . . . . . . . .. 4
B. Software ....................................................... ".............. 5
1. Data. Representations in the Computer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 5
2. Input/ Output Data Representations ............................. ". . . . . . . . . . . . .. 7
3. The Four Types of HP Interfaces. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . .. 7
4. The Data Transfer Process. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... . . . . . . . . . . . .. 9
C. Hardware ...................................................... , ............. 10
1. Logic Levels and TTL Implementations ......................... ~ ............. 10
2. Gates, Latches, and Flipflops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . 12
3. The Use of Jumpers ......................................... ".............. 15
II. Programming for Interfacing Operations ..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 17
A. Standard I/O Programming .................................................... 17
1. Register Operational Model of an Interface .................................... 17
2. Select Codes ............................................................. 18
3. Direct Register Access . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 18
4. Binary I/O Operations ..................................................... 19
5. Fomlatted I/O Operations .................................................. 19
6. The Status and Control Registers ............................................ 21
B. Interrupt I/O Programming ..................................................... 21
1. The Uses of Interrupt ...................................................... 21
2. Data Transfers with Slow Devices ............................................ 22
3. Further Data Transfer Examples ............................................. 24
4. Data Transfers with Fast Devices ............................................. 26
5. User Programmed SelVice Routines .......................................... 27
6. Interrupt Priorities ......................................................... 29
C. Special Programming Topics .................................................... 31
1. Fomlatting the Internal Printer and Display .................................... 31
2. Interface ID and Card Types ................................................ 32
3. Using Strings as Buffers .................................................... 32
4. Buffer Use Outside of the I/O Process ........................................ 33
5. Use of the Control Register ................................................. 34
III. HP Interface Cards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
A. Interfacing and the Computer I/O Bus ........................................... 37
B. The 980~~2A Bit Parallel Interface ................................................ 39
1. Gen(~ral Operational Characteristics .......................................... 39
2. The Handshake Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
3. Word and Byte Modes of Operation .......................................... 44
4. Data Inversion and the Transfer Process ....................................... 46
C. The 98033A BCD Interface ..................................................... 46
1. BCD Instruments .......................................................... 46
2. 98033A BCD Formats ..................................................... 47
3. The 98033A Interface Registers .............................................. 48
4. The 98033A Handshake Process ............................................ 49
5. Connecting BCD Devices to the 98033A ...................................... 49
D. The 98034A HP-IB Interface .................................................... 50
1. An Introduction to the HP-IB ................................................ 50
2. The Structure of the HP-IB ................................................. 50
3. Addressing Bus Devices .................................................... 51
4. Data Operations on the HP-IB ............................................... 53
5. Extended HP-IB Control Features ............................................ 54
6. Using the 98034A Interface ................................................. 57
E. The 98036A Serial I/O Interface ................................................ 61
1. An Introduction to Serial I/O ............................................... 61
2. Data Transmission Using Serial I/O .......................................... 62
3. Control Lines and the RS-232-C Standard ..................................... 65
4. The 98036A Serial I/O Interface ............................................ 66
5. Programming with the 98036A Interface ...................................... 72
6. RS-232-C vs. Current Loop Operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
Appendix .................................... , ............ " .... " .... " .......... " 75
A. ASCII Character Set ........................................................... 75
B. 98032A Register Map .......................................................... 77
98032A Jumper Options ....................................................... 78
C. 98033A Register Map .......................................................... 79
98033A Switch Configurations .................................................. 80
98033A Handshake Diagram ................................................... 80
D. 98034A Register Map .......................................................... 81
E. 98034A Operational Sequences ................................................. 82
F. 98036A Register Map .......................................................... 84
G. Keyboard / Display / Printer Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
H. Interfacing Bibliography ........................................................ 87
Index ... '" ...................... '" .......... " .... " .............................. 89
RE~ader's (.uide
This Huide for interfacing peripheral devices to to the 9825A with the HPL s1atements replaced by
Hewlett-Packard desktop computers is designed to their BASIC language eqUivalents.
provide additional information which may be helpful
to the user who needs to interface his peripheral Section I of this gUide presents general background
equipment to HP desktop computers and/or program information useful for interfacmg applications. For
the resultant system for interfacing applications. the engineer not experienced in software concepts,
information is given on computer data representa-
It is not intended to be a replacement for either the tions and I/O (input/output) programming. For the
operating and programming manuals for the desktop programmer not experienced in hardware concepts,
computer, or the installation and service manuals topics such as logic levels, TTL gates, latches, and
for the individual interface cards. The maximum flip-flops are discussed. The r(!ader with a
benefit can be obtained from this guide if these in- background in hardware and software can proceed
dividual manuals are studied first. They provide the directly to Section II.
user with a detailed description of the individual
operations available from the computer, and of the In Section II, the discussion is centered around pro-
various functions provided by each interface card. gramming for interfacing applications. It is not the
At th~ same time they assume that the user has a purpose of this section to teach the HPL program-
certain level of knowledge about the programming m ing language or to present the detailed syntax and
techniques (software) and electronics (hardware) in- restrictions of those programming statements
volved in interfacing applications. related to I/O operations. This is the purpose of the
operating manuals. Instead, the gUide tries to give
The purpose of this interfacing gUide is twofold. the user an appreciation for what takes place on the
First, it is intended to provide some introductory low level when the high level programming
hardware and software concepts which are assum- statements are executed. It is the philosophy of this
ed by the manuals, but with which the user may not gUide that if the user understands these low level
have previous experience. The second purpose of operations, many of the obselvations that appear to
the guide is to present an alternative approach to be strange from the high level will lose much of
explaining the operations discussed in these their mystery. Also, such an linderstanding should
manuals. For example, while the computer allow the reader to make more intelligent use of the
operating manual discusses the use and the detail- power available in desktop computer systems.
ed syntax of those programming statements
associated with interrupt operations, the gUide ex- Section III concentrates on the individual interface
pands. this information by discussing how interrupts cards themselves. Here again, an alternative ap-
are implemented, and when they should and should proach to the installation and service manuals for
not be used. The guide also presents introductory these cards is taken, and a re~~ister-operational
information on such topics as the Hewlett-Packard model of these interfaces is df