MARCH 1998 IC026A-R2 IC026AE-R2 RS-232↔IEEE 488 Interface Converter ER R N TALK CUSTOMER SUPPORT INFORMATION LISTE SRQ ERRO POW Order toll-free in the U.S. 24 hours, 7 A.M. Monday to midnight Friday: 877-877-BBOX FREE technical support, 24 hours a day, 7 days a week: Call 724-746-5500 or fax 724-746-0746 Mail order: Black Box Corporation, 1000 Park Drive, Lawrence, PA 15055-1018 Web site: www.blackbox.com • E-mail: info@blackbox.
RS-232↔IEEE 488 INTERFACE CONVERTER EUROPEAN UNION DECLARATION OF CONFORMITY To maintain safety, emission, and immunity standards of this declaration, the following conditions must be met. • Serial and IEEE cables must have a braided shield connected circumferentially to their connectors’ metal shells. • All cable screw locks must be tightened at both ends of the cable. • The host computer must be properly grounded. • Some inaccuracy is to be expected when I/O leads are exposed to RF fields or transients.
WARNING! Noted conditions pertain to potential safety hazards. When you see a WARNING!, CAUTION!, or IMPORTANT! note, carefully read the information and be alert to the possibility of personal injury. Failure to follow these directives voids emission and immunity compliance. TRADEMARKS USED IN THIS MANUAL AT ®, IBM®, and PS/2® are registered trademarks, and PC/XT is a trademark, of IBM Corporation. Macintosh® is a registered trademark of Apple Computer, Inc.
RS-232↔IEEE 488 INTERFACE CONVERTER FEDERAL COMMUNICATIONS COMMISSION AND INDUSTRY CANADA RADIO FREQUENCY INTERFERENCE STATEMENTS This equipment generates, uses, and can radiate radio frequency energy and if not installed and used properly, that is, in strict accordance with the manufacturer’s instructions, may cause interference to radio communication.
NOM STATEMENT NORMAS OFICIALES MEXICANAS (NOM) ELECTRICAL SAFETY STATEMENT INSTRUCCIONES DE SEGURIDAD 1. Todas las instrucciones de seguridad y operación deberán ser leídas antes de que el aparato eléctrico sea operado. 2. Las instrucciones de seguridad y operación deberán ser guardadas para referencia futura. 3. Todas las advertencias en el aparato eléctrico y en sus instrucciones de operación deben ser respetadas. 4. Todas las instrucciones de operación y uso deben ser seguidas. 5.
RS-232↔IEEE 488 INTERFACE CONVERTER 11. El aparato eléctrico deberá ser connectado a una fuente de poder sólo del tipo descrito en el instructivo de operación, o como se indique en el aparato. 12. Precaución debe ser tomada de tal manera que la tierra fisica y la polarización del equipo no sea eliminada. 13.
CONTENTS Contents Chapter Page 1. Specifications..................................................................................................10 2. Introduction ...................................................................................................12 2.1 Description ............................................................................................12 2.2 Abbreviations .........................................................................................13 3. Getting Started ..
RS-232↔IEEE 488 INTERFACE CONVERTER Chapter Page 4.4 Talk-Back Features ................................................................................34 4.4.1 Talk-Back on Terminator..........................................................34 4.4.2 Talk-Back on Timeout...............................................................36 4.5 Plotter Applications...............................................................................38 4.6 Printer Applications ..........................................
CONTENTS Chapter Page 6.5 Handshake Lines...................................................................................57 6.5.1 Data Valid (DAV).......................................................................57 6.5.2 Not Ready For Data (NRFD) ....................................................57 6.5.3 Not Data Accepted (NDAC) .....................................................57 6.6 Data Lines ..............................................................................................
RS-232↔IEEE 488 INTERFACE CONVERTER 1. Specifications IEEE-488 Interface Implementation — C1, C2, C3, C4, and C28 controller subsets. Serial to IEEE: SH1, AH1, T6, TE0, L4, LE0, SR1, RL0, PP0, DC1, DT0, E1. Terminators — Selectable CR, LF, LF-CR, and CR-LF with EOI Connector — Standard IEEE 488 connector with metric studs Serial Interface 10 EIA RS-232C — AB, BA, BB, CA, CB EIA RS-422A — Balanced voltage on TxD and RxD Character Set — Asynchronous bit serial Output Voltage — ±5 volts min.
CHAPTER 1: Specifications General Data Buffer — 32,000 characters dynamically allocated Indicators — LEDs for IEEE Talk and Listen, Serial Send and Receive, and Power Power — 105-125V or 210-250V; 50-60 Hz, 10 VA max. Size — 2.7"H x 5.5"W x 7.4"D (6.9 x 14 x 18.8 cm) Weight — 3.6 lb. (1.6 kg) Environment — 0 to 50°C; 0 to 70% R.H. to 35°C. Linearly derate 3% R.H./degrees Centigrade from 35 to 50°C Controls — Power Switch (external), IEEE and Serial parameter switches (internal).
RS-232↔IEEE 488 INTERFACE CONVERTER 2. Introduction 2.1 Description The RS-232↔488 Interface Converter provides transparent communication from a serial computer to an IEEE 488 printer, plotter, or other device. It also can be used to control a serial device, such as a printer or terminal, from an IEEE 488 host computer. As a serial-to-IEEE-488 converter, the interface converter receives data from a serial host then automatically performs the bus sequences necessary to send this data to the IEEE 488 device.
CHAPTER 2: Introduction 2.2 Abbreviations The IEEE 488 abbreviations listed below are used throughout this manual.
RS-232↔IEEE 488 INTERFACE CONVERTER 3. Getting Started 3.1 Inspection The interface converter was carefully inspected, both mechanically and electrically, prior to shipment. When you receive it, carefully unpack all items from the shipping carton and check for any obvious signs of damage that may have occurred during shipment. Immediately report any damage found to the shipping agent. Remember to retain all shipping materials in the event that shipment back to the factory becomes necessary.
CHAPTER 3: Getting Started DOT SW3 1 2 3 4 5 6 7 8 Switch Side View OPEN 10 IEEE Addr LF IEEE Term EOI Disabled DOT SW2 1 2 3 4 5 6 7 8 Switch Side View OPEN Mode Talk-Back on Timeout Serial Term Echo Parity C Enabled LF No Echo No Parity DOT SW1 1 2 3 4 5 6 7 8 Switch Side View OPEN Baud Rate Handshake Word Length Talk-Back on Term Stop Bits 9600 RTS/CTS 8 Data Bits Enabled 2 Stop Bits Figure 3-1. Factory-Default Settings.
RS-232↔IEEE 488 INTERFACE CONVERTER Note that the interface converter comes configured as an IEEE controller. In this mode, the interface converter is designed to allow an RS-232 computer to communicate with an IEEE peripheral such as a plotter. This controller mode is described in detail in Chapter 4. The interface converter may also be configured as an IEEE peripheral. As an IEEE peripheral, it allows an IEEE controller to communicate with an RS-232 device.
CHAPTER 3: Getting Started 1 2 3 4 5 6 7 8 110 Switch Side View 1800 OPEN OPEN 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 110 DOT 1 2 3 4 5 6 7 8 2400 OPEN OPEN 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 110 3600 OPEN OPEN 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 135 4800 OPEN OPEN 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 15 0 7200 OPEN OPEN 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 9600 300 OPEN OPEN 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 600 19,200 OPEN OPEN 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1200 57,600 OPEN OPEN Figure
RS-232↔IEEE 488 INTERFACE CONVERTER 3.3.2 SERIAL WORD LENGTH (DATA BITS) SW1-6 determines the number of data bits, often referred to as word length, for each serial character transmitted or received. The factory default is 8 data bits. 1 2 3 4 5 6 7 8 DOT 1 2 3 4 5 6 7 8 Switch Side View OPEN OPEN 8 Data Bits 7 Data Bits Figure 3-3. Switch SW1: Selecting the Serial Word Length (Data Bits). 3.3.
CHAPTER 3: Getting Started 3.3.4 SERIAL PARITY Serial Parity is selected with S2-6 through S2-8. The interface converter generates the selected parity during serial transmissions but it does not check parity on data that is received. The factory default is parity disabled. 1 2 3 4 5 6 7 8 DOT 1 2 3 4 5 6 7 8 Switch Side View OPEN OPEN Odd Parity Mark Parity 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 OPEN OPEN Even Parity Space Parity 1 2 3 4 5 6 7 8 OPEN Parity Disabled Figure 3-5.
RS-232↔IEEE 488 INTERFACE CONVERTER 3.3.6 SERIAL HANDSHAKE Switch SW1-5 is used to select hardware [RTS/CTS] or software [Xon/Xoff] serial handshake control. With X-ON/X-OFF, the interface converter issues an X-OFF character [ASCII value of $13] when its buffer memory is near full. When the X-OFF character is sent, there are still more than 1000 character locations remaining to protect against buffer overrun.
CHAPTER 3: Getting Started 3.4 Selecting Terminator Substitution The interface converter can be configured to provide RS-232-to-IEEE-488 and IEEE-488-to-RS-232 terminator substitution. This is useful when interfacing an RS-232 device which only issues carriage return [CR] as an output terminator to an IEEE controller which expects a carriage return followed by a line feed [CR-LF]. In a case like that, the serial terminator should be selected for CR Only while the IEEE terminator is set to CR-LF.
RS-232↔IEEE 488 INTERFACE CONVERTER 3.4.2 IEEE BUS TERMINATOR SW3-6 through SW3-8 set the IEEE bus terminators used for data sent or received by the interface converter. EOI, a line used to signal the end of a multiple character bus transfer, may also be enabled. If enabled, EOI is asserted when the last selected bus terminator is sent. Factory default is LF Only with EOI disabled.
CHAPTER 3: Getting Started 1 2 3 4 5 6 7 8 DOT 1 2 3 4 5 6 7 8 Switch Side View OPEN OPEN Controller Mode Peripheral Mode Figure 3-10. Switch SW2: Selecting the Mode. 3.6 Selecting the IEEE Address SW3-1 through SW3-5 select the IEEE bus address of the interface converter when in the IEEE Peripheral mode. These same switches are used in the IEEE Controller mode to select the address of the device that will be controlled. [Refer to Chapters 5 and 4 respectively for additional information].
RS-232↔IEEE 488 INTERFACE CONVERTER 3.7 Feature Selections The functions of the remaining switches are dependent on the mode selected. A brief description of each of these features follows. You should refer to the listed sections for additional information. 3.7.1 CONTROLLER FEATURES In the IEEE Controller (RS-232-to-IEEE 488 Converter) mode, SW1-7 is used to determine whether the interface should, after sending the IEEE bus terminators, address the attached bus device to talk.
CHAPTER 3: Getting Started 3.7.2 PERIPHERAL FEATURES In the IEEE Peripheral (IEEE 488 to RS-232 converter) mode, SW1-7 enables the interface to assert the SRQ IEEE bus interface line to indicate that it has received the last switch selected serial terminator character from the serial device. 1 2 3 4 5 6 7 8 DOT 1 2 3 4 5 6 7 8 Switch Side View OPEN OPEN SRQ on Last Terminator Disabled SRQ on Last Terminator Enabled Figure 3-14.
RS-232↔IEEE 488 INTERFACE CONVERTER 3.8.1 RS-232/RS-422 SIGNAL LEVEL SELECTION The interface converter’s factory default signal levels are compatible with RS-232. To select RS-422 levels, carefully remove the 8-position shorting plug with a small flat blade screwdriver from J106. Install the DIP jumper into J205 making certain that all of the pins on the shorting plug are inserted correctly. Shorting Plug RS-422 RS-232 Figure 3-15. Selecting RS-232 or RS-422 Signal Levels. 3.8.
+RXD 25 +TXD GND +VTEST RTS CTS -TXD -RXD 13 +VTEST CHAPTER 3: Getting Started 1 14 Figure 3-16. Rear View of the Interface Converter’s Serial Connector. -RxD Receive Data—Input—Pin 2 This pin accepts serial data sent by the RS-232 or RS-422 host. The serial data is expected with the word length, baud rate, stop bits, and parity selected by the internal switches. The signal level is low true. -TxD Transmit Data—Output—Pin 3 This pin transmits serial data to the RS-232 or RS-422 host.
RS-232↔IEEE 488 INTERFACE CONVERTER Vtest Test Voltage—Output—Pin 6 This pin is connected to +5 volts through a 1K resistor. It is also common to Vtest on Pin 9. Gnd Ground—Pin 7 This pin sets the ground reference point for the other RS-232 inputs and outputs. Vtest Test Voltage—Output—Pin 9 This pin is connected to +5 volts through a 1K resistor. It is also common to Vtest on Pin 6. +RxD Receive Data Plus—Input—Pin 14 This pin accepts serial data sent by the RS-422 host.
CHAPTER 3: Getting Started 3.8.3 SERIAL-CABLE WIRING DIAGRAMS If a cable was not purchased with the interface, the following diagrams will be helpful in making your own cable. Simple soldering skills and an attention to detail will ensure successful construction. Mini DINs Male RTS CTS -TxD Gnd -RxD +TxD +RxD DB25 Male 4 CTS 5 RTS 2 -RxD 7 Gnd 3 -TxD 14 +RxD 16 +TxD 1 2 3 4 5 6 8 Figure 3-17. Wiring Diagram: Macintosh to Interface Converter (RS-422).
RS-232↔IEEE 488 INTERFACE CONVERTER DB9 Female DCD -RxD -TxD DTR Gnd DSR RTS CTS DB25 Male 1 2 3 4 5 6 7 8 3 -TxD 2 -RxD 7 Gnd 4 CTS 5 RTS Figure 3-19. Wiring Diagram: IBM AT or Compatible with DB9 Serial Connector to Interface Converter (RS-232). NOTE Standard AT 9-pin-to-25-pin adapter cables are not wired as shown above and will not work with the interface converter. 3.9 General Refer to the following sections for specific operational modes. This subsection gives a general test of functionality.
CHAPTER 3: Getting Started After plugging the power-supply connector into the interface, plug the power supply into AC line power. Turn the rear-panel power switch ON (the “1” position). All the front-panel indicators should light momentarily while the interface converter performs an internal ROM and RAM self-check. At the end of this self-check, all indicators except POWER should turn off. If there is an error in the ROM checksum, all of the LEDs will remain on. Flashing LEDs indicate a RAM failure.
RS-232↔IEEE 488 INTERFACE CONVERTER 4. Controller Operation 4.1 Controller-Mode (Serial to IEEE) Operation The IEEE Controller mode allows a serial RS-232 or RS-422 host device to send data to a single IEEE bus peripheral or to multiple peripherals if they occupy the same bus address. Applications include interfacing a listen-only or addressable IEEE printer/plotter to a serial printer port. Once the interface converter has initialized itself after power-on, it waits for serial input data.
CHAPTER 4: Controller Operation 4.2 Serial and IEEE Terminator Substitution The interface converter can be configured to provide serial-to-IEEE-488 and IEEE-488-to-serial terminator substitution. This is useful when interfacing a serial host which only issues carriage return [CR] as an output terminator to an IEEE peripheral which expects a carriage return followed by a line feed [CR-LF]. In this case, the serial terminator should be selected for CR Only while the IEEE terminator is set for CR-LF.
RS-232↔IEEE 488 INTERFACE CONVERTER 4.3 IEEE Address Selection SW3-1 through SW3-5 select the IEEE bus address of the IEEE peripheral the interface converter will be communicating with. These switches set the address of the IEEE device that will be controlled, not the address of the interface converter. The address of the interface converter is automatically adjusted so that address conflicts will not occur.
CHAPTER 4: Controller Operation 1 2 3 4 5 6 7 8 DOT 1 2 3 4 5 6 7 8 Switch Side View OPEN OPEN Talk-Back on Terminator Disabled Talk-Back on Terminator Enabled Figure 4-2. Switch SW1: Enabling or Disabling “Talk-Back on Terminator.” When the serial input buffer becomes empty, the interface converter checks the last characters sent to the IEEE bus device. If these were the IEEE bus terminators and Talk-Back on Terminator is enabled, the IEEE bus device is addressed to talk.
RS-232↔IEEE 488 INTERFACE CONVERTER 4.4.2 TALK-BACK ON TIMEOUT SW2-2 selects whether the interface converter should address the attached bus device to talk when the interface converter has no more serial data to send. This feature relies on time and not on terminators. Its use is primarily for simulating a serial plotter from an IEEE 488 (HP-IB) plotter. The factory default is Talk-Back On Timeout enabled.
CHAPTER 4: Controller Operation The following is an example of how this feature can be used to communicate with an IEEE plotter. The program example is written in BASIC on an IBM PC or compatible. It turns the PC into a dumb serial terminal. When a key is pressed on the keyboard, the character is transmitted out of the serial (COM1) port. Any serial data which is received from the port is printed on the display.
RS-232↔IEEE 488 INTERFACE CONVERTER 4.5 Plotter Applications To use the interface converter to interface an HP-IB plotter to a serial computer port, you will need the following information about your system: 1) The serial data format that the application (plotting or graphics) program expects the plotter to communicate with. These parameters include baud rate, word length, stop bits, parity and serial control. Some programs allow these parameters to be selected by the user.
CHAPTER 4: Controller Operation RS-232 IEEE 488 Interface Converter Figure 4-4. A PC-Based Graphics System. The following shows the interface converter’s internal switch settings required to use a Hewlett-Packard 7580A plotter with AutoCAD® from AUTODESK on an IBM PC or compatible. Because PCs and compatibles output RS-232 levels, the shorting DIP jumper should be set to the RS-232 position (J206). Shorting Plug RS-422 RS-232 Figure 4-5. Selecting RS-232 Signal Levels.
RS-232↔IEEE 488 INTERFACE CONVERTER DOT SW3 1 2 3 4 5 6 7 8 Switch Side View OPEN 5 IEEE Addr CR Only IEEE Term EOI Enabled DOT SW2 1 2 3 4 5 6 7 8 Switch Side View OPEN Mode Talk-Back on Timeout Serial Term Echo Parity C Enabled CR No Echo Even DOT SW1 1 2 3 4 5 6 7 8 Switch Side View OPEN Baud Rate Handshake Word Length Talk-Back on Terminator Stop Bits 9600 X-ON/X-OFF 7 Data Bits Enabled 1 Stop Bit Figure 4-6. Interface Converter Settings for Use with HP 7580A Plotter on an IBM PC.
CHAPTER 4: Controller Operation File Edit Windows Settings for HP 7500A Baud Rate: 57600 Stop Bits: 1 Parity: None Paper Si Apple Plotter Graphic MP31 / 2 / 300 Houst Calcomp 104x/7x,9x5 H.P. 7220 Houst Calcomp 81 H.P. 7440A ColorPro Houst Colorwriter 6200DS10 H.P. 7470A Houst Colorwriter 6310 H.P. 7475 Houst Colorwriter 6320 H.P. 7550A Houst Epson HI-80 H.P. 7570A DraftPro Houst Facit 4551 H.P. 7580B Houst Graphtec FP5301 H.P. 7585B Houst Figure 4-7.
RS-232↔IEEE 488 INTERFACE CONVERTER Shorting Plug RS-422 RS-232 Figure 4-9. Setting the Internal DIP Shorting Jumper for RS-422. The following illustrates the interface converter’s internal switch settings for use with MacPlot, using the previously described format.
CHAPTER 4: Controller Operation DOT SW3 1 2 3 4 5 6 7 8 Switch Side View OPEN 5 IEEE Addr CR IEEE Term EOI Enabled DOT SW2 1 2 3 4 5 6 7 8 Switch Side View OPEN Mode Talk-Back on Timeout Serial Term Echo Parity C Enabled CR No Echo No Parity DOT SW1 1 2 3 4 5 6 7 8 Switch Side View OPEN Baud Rate Handshake Word Length Talk-Back on Terminator Stop Bits 57600 X-ON/X-OFF 7 Data Bits Enabled 1 Stop Bit Figure 4-10. Interface Converter Settings for Use with HP 7580A Plotter on a Macintosh.
RS-232↔IEEE 488 INTERFACE CONVERTER 4.6 Printer Applications Most of the information given for plotter applications applies to applications for interfacing IEEE 488 printers to a serial host. Some high-end printers have a secondary command setting which must be disabled for the interface converter to control them. The interface converter does not use secondary commands to control IEEE peripherals, such as printers or plotters.
CHAPTER 5: Peripheral Operation 5. Peripheral Operation 5.1 Peripheral-Mode Operation This mode of operation is useful in interfacing a serial device, such as a serial printer, plotter or instrument, to an IEEE controller. Data which is sent by the IEEE controller to the interface converter is buffered and transmitted out its serial port. Data received from the serial device is buffered by the interface converter until read by the IEEE controller.
RS-232↔IEEE 488 INTERFACE CONVERTER When more than 10 queues become available, it asserts RTS or issues “X-ON.” The IEEE bus input signals that the IEEE input (or serial output) buffer is full when the number of queues available drops below 10 (1280 character locations left). When the number of available queues drops to 4 or less (512 character locations left), the IEEE interface of the interface converter stops accepting data from the bus.
CHAPTER 5: Peripheral Operation 5.3.2 CONTROLLED BUS DATA TRANSFERS If the controller must avoid waiting for the serial device, it can “serial-poll” the interface converter. Serial polling is a method by which the controller can inquire the internal status of the interface without disturbing any data being transferred, slowing data transfers, or locking up the bus. You should refer to the programming manual of your controller to determine the method of performing serial polls.
RS-232↔IEEE 488 INTERFACE CONVERTER 1 2 3 4 5 6 7 8 DOT 1 2 3 4 5 6 7 8 Switch Side View OPEN OPEN SRQ on Last Terminator Disabled SRQ on Last Terminator Enabled Figure 5-1. Switch SW1: Enabling or Disabling “SRQ on Last Terminator.” 5.4 Serial-Poll Status-Byte Register The following shows and describes the serial-poll status information provided by the interface converter.
CHAPTER 5: Peripheral Operation DIO7 rsv serial-poll status information This bit is defined by the IEEE 488 Specification and is used to indicate to the bus controller that the interface converter is the bus device that requested service. It is cleared when the interface is serial polled by the controller. DIO6 Not Defined—Always “0” DIO5 Serial Input Buffer NOT EMPTY This bit is set when the serial input buffer contains one or more data bytes which have not been sent out the IEEE bus.
RS-232↔IEEE 488 INTERFACE CONVERTER 5.5 Use of Serial and Bus Terminators The interface converter can be configured to provide RS-232-to-IEEE-488 and IEEE-488-to-RS-232 terminator substitution. This is useful when interfacing a serial device that only issues carriage return [CR] as an output terminator to an IEEE controller that expects a carriage return followed by a line feed [CR-LF]. In this previous example, the serial terminator should be selected for CR Only while the IEEE terminator is set to CR-LF.
CHAPTER 5: Peripheral Operation 5.6.1 MY TALK ADDRESS (MTA) When the interface converter is addressed to talk, it retrieves data from the serial input buffer and outputs it to the IEEE 488 bus. It substitutes the selected IEEE bus terminators for the received serial terminators. The interface converter will continue to output serial input buffer data as long as the IEEE controller allows. 5.6.
RS-232↔IEEE 488 INTERFACE CONVERTER 5.7 IEEE Address Selection SW3-1 through SW3-5 select the IEEE bus address of the interface converter when in the IEEE Peripheral mode. The address is selected by simple binary weighting with SW3-1 being the least significant bit and SW3-5 the most significant. The following figure shows the IEEE address of the interface converter set to 10. 0 DOT 1 2 3 4 5 6 7 8 Switch Side View 1 OPEN 0 x 16 -0 1x8 -8 0x4 -0 1x2 -2 0 x 1 + -0 IEEE Address = 10 Figure 5-3.
CHAPTER 6: IEEE 488 Primer 6. IEEE 488 Primer 6.1 History The IEEE 488 bus is an instrumentation-communication bus adopted by the Institute of Electrical and Electronic Engineers in 1975 and revised in 1978. The interface converter conforms to this most recent revision, designated IEEE 488-1978. Before this standard was adopted most instrumentation manufacturers offered their own versions of computer interfaces. This placed the burden of system hardware design on the end user.
RS-232↔IEEE 488 INTERFACE CONVERTER At a committee meeting, everyone present usually listens. This is not the case with the GPIB. The Active Controller selects which devices will listen and commands all other devices to ignore what is being transmitted. A device is instructed to listen by being Addressed to Listen. This device is then referred to as an Active Listener. Devices that are to ignore the data message are instructed to Unlisten. The reason some devices are instructed to Unlisten is quite simple.
CHAPTER 6: IEEE 488 Primer To Other Devices Device 1 System Controller Able to Talk, Listen, and Control Data Bus Device 2 DMM Able to Talk and Listen Data Byte Transfer Control Device 3 Printer Only Able to Listen General Interface Management Device 4 Frequency Counter Only Able to Talk DIO1-8 DAV NRFD NDAC IFC ATN SRQ REN EOI Figure 6-1. IEEE 488 Bus Structure. 6.3 Send It to My Address In the previous discussion, the terms “Addressed to Talk” and “Addressed to Listen” were used.
RS-232↔IEEE 488 INTERFACE CONVERTER 6.4 Bus Management Lines Five hardware lines on the GPIB are used for bus management. Signals on these lines are often referred to as uniline (single line) commands. The signals are “active low”: A low voltage represents a logical “1” (asserted), and a high voltage represents a logical “0” (unasserted). 6.4.1 ATTENTION (ATN) ATN is one of the most important lines for bus management.
CHAPTER 6: IEEE 488 Primer 6.5 Handshake Lines The GPIB uses three handshake lines in an “I’m ready—Here’s the data—I’ve got it” sequence. This handshake protocol assures reliable data transfer, at the rate determined by the slowest Listener. One line is controlled by the Talker, while the other two are shared by all Active Listeners. The handshake lines, like the other IEEE 488 lines, are active low. 6.5.1 DATA VALID (DAV) The DAV line is controlled by the Talker.
RS-232↔IEEE 488 INTERFACE CONVERTER 1st Data Byte 2nd Data Byte DIO-8 (composite) DAV Source Valid NFRD Acceptor All Ready NDAC Acceptor None Accept Not Valid None Ready All Accept All Ready Valid Not Valid None Ready None Accept All Accept Figure 6-2. IEEE Bus Handshaking. 6.6 Data Lines The GPIB provides eight data lines for a bit-parallel/byte-serial data transfer. These eight data lines use the convention of DIO1 through DIO8 instead of the binary designation of D0 to D7.
CHAPTER 6: IEEE 488 Primer 6.7.3 UNLISTEN (UNL) This command tells all bus devices to Unlisten. The same as Unaddressed to Listen. ($3F) 6.7.4 TALK ADDRESS GROUP (TAG) There are 31 (0 to 30) talk addresses associated with this group. The 3 most significant bits of the data bus are set to 010 while the 5 least significant bits are the address of the device being told to talk. 6.7.5 UNTALK (UNT) This command tells bus devices to Untalk. The same as Unaddressed to Talk. ($5F) 6.7.
RS-232↔IEEE 488 INTERFACE CONVERTER 6.7.12 TAKE CONTROL (TCT) This command passes bus control responsibilities from the current Controller to another device which has the ability to control. ($09 ) 6.7.13 SECONDARY COMMAND GROUP (SCG) These are any one of the 32 possible commands (0 to 31) in this group. They must immediately follow a talk or listen address. ($60 to $7F) 6.7.
CHAPTER 6: IEEE 488 Primer 6.8.1 SERIAL POLL Suppose the Controller receives a service request. For this example, let’s assume there are several devices which could assert SRQ. The Controller issues an SPE (Serial Poll enable) command to each device sequentially. If any device responds with DIO7 asserted, it indicates to the Controller that it was the device that asserted, SRQ. Often the other bits will indicate why the device wanted service.
RS-232↔IEEE 488 INTERFACE CONVERTER 7. Theory of Operation and Board Layout 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)].
CHAPTER 7: Theory of Operation and Board Layout 7.2 Board Layout D103 D104 D105 D106 D102 R104 U113 U104 C113 C104 U105 C105 R101 D101 J104 U103 C110 C103 U110 C102 U102 C117 C118 Y101 C101 U101 R102 C124 C106 U106 C107 C108 U107 U108 J101 Figure 7-1. Component Layout of the Interface Converter’s Motherboard.
RS-232↔IEEE 488 INTERFACE CONVERTER U201 S201 SW1 P204 R205 C202 S202 SW2 U206 C210 R202 U202 C201 C206 R201 U205 + S203 SW3 U203 C205 C207 U208 R207 1 14 C208 S205 J204 Figure 7-2. Component Layout of the Interface Converter’s Serial I/O board.
APPENDIX A: Sample Dumb-Terminal Program Appendix A.
RS-232↔IEEE 488 INTERFACE CONVERTER Appendix B. Character Codes and IEEE Multiline Messages $00 0 $10 NUL $01 16 $20 DLE 00 17 $21 1 $11 SOH DC1 LLO 2 $12 GTL $02 STX $03 $04 EOT DC4 ENQ PPC $06 NAK 05 22 $26 PPU 6 $16 ACK $07 SYN $08 HT EM LF $0B $0C ESC FS SO $0F , GS RS 28 45 $3D 15 $1F SI US ACG UCG .
APPENDIX B: Character Codes and IEEE Multiline Messages How To Read the Chart Hexadecimal Equivalent Decimal Equivalent ASCII Character Address or Command 67
RS-232↔IEEE 488 INTERFACE CONVERTER Index Abbreviations IEEE 488 .................................13 Active Controller ...........................53 Address Selection IEEE ........................................34 Applications Plotter .....................................38 Printer .....................................44 ATN ................................................56 Attention ........................................56 Baud Rate.......................................16 Blind Bus Data Transfers ...
INDEX Interface Clear .........................51, 56 Interface Converter Connectors.....................................26 Introduction...................................12 LAG ................................................58 LEDs ...................................31, 37, 43 Listen Address Group....................58 Listen Only...............................23, 52 LLO ................................................59 Local Lockout ................................59 MLA.................................
RS-232↔IEEE 488 INTERFACE CONVERTER Serial Parity ....................................18 Serial Poll .......................................61 Serial Poll Disable....................51, 59 Serial Poll Enable ....................51, 59 Serial Port Settings ........................16 Serial Signal Descriptions .............26 Serial Terminator ..........................21 Serial-Poll Status Information..............................48, 49 Serial-Poll Status-Byte Register........................................
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