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Black Box IC026A-R2, IC026AE-R2 7. Theory of Operation and Board Layout

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RS-232↔IEEE 488 INTERFACE CONVERTER

7.1 Theory of Operation

The heart of the interface converter is a 6809 microprocessor (U101)

supported by 8K bytes of firmware EPROM [U102 (2764)] and 32K bytes of

static RAM [U103 (58256)]. A Versatile Interface Adapter [U104 (65B22)]

is used to generate real-time interrupts for the firmware operating system.

The front-panel annunciators are also driven by U104 through an inverter

[U113 (74LS04)]. The IEEE 488 bus interface is accomplished by a

TMS9914A [U106] controller with drivers U107 and U108. The serial

interface is provided by the UART [6551 (U105)]. If RS-232 levels are chosen,

they are provided by the RS-232 transceiver (U209). If RS-422 levels are

selected, the differential driver [26LS30 (U207)] and receiver [26LS33

(U208)] are used.

The internal DIP switches [SW1, SW2, and SW3] are read via 74HCT244

tri-state buffers [U201, U202 and U203]. Power is supplied by an external

unregulated 9-volt wallmount supply. Regulation to the required +5 volts is

provided by U206 [7805].

Decoding of the microprocessor address space is accomplished with a

Programmable Logic Array [U110 (16L8)]. The Memory space allocation is:

Address Device Part Number Function

$0000-$7FFF U103 58258 Static RAM

$A000-$A007 U106 9914A IEEE Controller

$A800-$A807 U105 6551 UART

$B000-$B00F U104 65B22 VIA

$B800 U201 74HCT244 SW1 (S201)

$B801 U202 74HCT244 SW2 (S202)

$B802 U203 74HCT244 SW3 (S203)

$E000-$FFFF U102 2764 Programmed EPROM

7. Theory of Operation and Board Layout

Contents

Main RS-232IEEE 488 INTERFACE CONVERTER EUROPEAN UNION DECLARATION OF CONFORMITY WARNING! Failure to follow these directives voids emission and immunity compliance. Page Page Page CONTENTS Contents RS-232IEEE 488 INTERFACE CONVERTER CONTENTS 1. Specifications WARNING! CHAPTER 1: Specifications CAUTION 2. Introduction 2.1 Description 2.2 Abbreviations CHAPTER 2: Introduction 3. Getting Started 3.1 Inspection 3.2 Configuration Figure 3-1. Factory-Default Settings. SW3 SW2 SW1 3.3 Serial Port Settings Figure 3-2. Switch SW1: Selecting the Serial Baud Rate. Figure 3-3. Switch SW1: Selecting the Serial Word Length (Data Bits). Figure 3-4. Switch SW1: Selecting the Serial Stop Bits. Figure 3-5. Switch SW2: Selecting the Serial Parity. Figure 3-6. Switch SW2: Enabling or Disabling Echo. Figure 3-7. Switch SW1: Selecting the Serial Handshake. 3.4 Selecting Terminator Substitution Figure 3-8. Switch SW2: Selecting the Serial Terminator. Figure 3-9. Switch SW3: Selecting the IEEE Bus Terminator. 3.5 Selecting the Mode Figure 3-10. Switch SW2: Selecting the Mode. 3.6 Selecting the IEEE Address Figure 3-11. Switch SW3: Selecting the IEEE Address. 3.7 Feature Selections Figure 3-12. Switch SW1: Enabling or Disabling Talk Back on Terminator in Controller Mode. Figure 3-13. Switch SW2: Enabling or Disabling Talk Back on Timeout in Controller Mode. Figure 3-14. Switch SW1: Enabling or Disabling SRQ on Last Serial Terminator in Peripheral Mode. 3.8 Serial Interface Figure 3-15. Selecting RS-232 or RS-422 Signal Levels. Figure 3-16. Rear View of the Interface Converters Serial Connector. Page Page 3.9 General CAUTION Page RS-232IEEE 488 INTERFACE CONVERTER 4.1 Controller-Mode (Serial to IEEE) Operation 4. Controller Operation 4.2 Serial and IEEE Terminator Substitution 4.3 IEEE Address Selection Figure 4-1. Switch SW3: Selecting the IEEE Address. 4.4 Talk-Back Features Figure 4-2. Switch SW1: Enabling or Disabling Talk-Back on Terminator. Figure 4-3. Switch SW2: Enabling or Disabling Talk-Back on Timeout. Page 4.5 Plotter Applications Figure 4-4. A PC-Based Graphics System. Figure 4-5. Selecting RS-232 Signal Levels. Figure 4-6. Interface Converter Settings for Use with HP 7580A Plotter on an IBM PC. SW2 SW3 SW1 Figure 4-7. MacPlot Configuration Screen. Figure 4-8. A Macintosh Based Graphics System. Interface Converter IEEE 488 RS-422 Page Figure 4-10. Interface Converter Settings for Use with HP 7580A Plotter on a Macintosh. Page 5. Peripheral Operation 5.1 Peripheral-Mode Operation 5.2 Serial and IEEE Input Buffers 5.3 IEEE Data Transfers Page RS-232IEEE 488 INTERFACE CONVERTER Figure 5-1. Switch SW1: Enabling or Disabling SRQ on Last Terminator. Figure 5-2. Serial Poll Status Byte. 5.4 Serial-Poll Status-Byte Register Page 5.5 Use of Serial and Bus Terminators 5.6 IEEE 488 Bus Implementation Page 5.7 IEEE Address Selection Figure 5-3. SW3 View for IEEE Address Selection. 6. IEEE 488 Primer 6.1 History 6.2 General Structure Page Figure 6-1. IEEE 488 Bus Structure. 6.3 Send It to My Address 6.4 Bus Management Lines 6.5 Handshake Lines Figure 6-2. IEEE Bus Handshaking. 6.6 Data Lines 6.7 Multiline Commands Page 6.8 More on Service Requests Page 7.1 Theory of Operation 7. Theory of Operation and Board Layout 7.2 Board Layout CHAPTER 7: Theory of Operation and Board Layout Figure 7-1. Component Layout of the Interface Converters Motherboard. Figure 7-2. Component Layout of the Interface Converters Serial I/O board. APPENDIX A: Sample Dumb-Terminal Program Appendix A. Sample Dumb-Terminal Program Appendix B. Character Codes and IEEE Multiline Messages Page Index INDEX