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IEEE 488 Primer

4.1  HISTORY

The IEEE 488 bus is an instrumentation communication bus adopted by the Institute
of Electrical and Electronic Engineers in 1975, revised in 1978 and revised and
extended in 1987.  The Digital488HS/32 conforms to this most recent revision
designated IEEE 488.1.

Prior to the adoption of this standard, most instrumentation manufacturers offered
their own versions of computer interfaces. This placed the burden of system hardware
design on the end user. If his application required the products of several different
manufacturers, then he might need to design several different hardware and software
interfaces.  The popularity of the IEEE 488 interface (sometimes called the General
Purpose Interface Bus or GPIB) is due to the total specification of the electrical and
mechanical interface as well as the data transfer and control protocols. The use of the
IEEE 488 standard has moved the responsibility of the user from design of the
interface to design of the high level software that is specific to the measurement
application.

4.2  GENERAL STRUCTURE

The main purpose of the IEEE 488.1 interface is to transfer information between two
or more devices.  A device can either be an instrument or a computer.  Before any
information transfer can take place, it is first necessary to specify which will do the
talking (send data) and which devices will be allowed to listen (receive data).  The
decision of who will talk and who will listen usually falls on the System Controller
which is, at power on, the Active Controller.

The System Controller is similar to a committee chairman.  On a well run
committee, only one person may speak at a time and the chairman is responsible for
recognizing members and allowing them to have their say.  On the bus, the device
which is recognized to speak is the Active Talker. There can only be one Talker at a
time if the information transferred is to be clearly understood by all. The act of
"giving the floor" to that device is called Addressing to Talk. If the committee
chairman can not attend the meeting, or if other matters require his attention, he can
appoint an acting chairman to take control of the proceedings. For the GPIB, this
device becomes the Active Controller.
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

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Содержание Digital HS

Страница 1: ...uy your excess underutilized and idle equipment along with credit for buybacks and trade ins Custom engineering so your equipment works exactly as you specify Critical and expedited services Leasing R...

Страница 2: ...440 439 4091 Fax 440 439 4093 E mail sales iotech com Internet http www iotech com Digital HS User s Manual p n Digital HS 901 1998 by IOtech Inc Printed in the United States of America Artisan Techn...

Страница 3: ...n of Conformity stating which specifications and operating conditions apply Warnings and Cautions Refer all service to qualified personnel This caution symbol warns of possible personal injury or equi...

Страница 4: ...ed to or from the second byte port with the IEEE 488 bus control line EOI as the 9th bit In the 16 bit mode the first eight bits of data are transferred to or from the first byte port followed by the...

Страница 5: ...1 An external input to the Digital488HS 32 serial poll register which can be read via IEEE 488 serial polls This condition may also be switch selected to generate an SRQ on the IEEE 488 bus SB2 Seria...

Страница 6: ...status bit lines clear output trigger output reset input input END of data and output END of data lines Logic Levels Output VOH 2 volts min IOH 15 mA 3 4 volts typ IOH 3 mA VOL 0 5 volts max IOL 24 mA...

Страница 7: ...Indicators LEDs for Talk Listen SRQ Input Port Full Output Port Empty and Power Power 105 125V or 210 250v 50 60 Hz 60 VA max Environment 0 to 50 C 0 to 70 RH to 35 C Linearly derate RH 3 C from 35 t...

Страница 8: ...e LAG Listen Address Group LF Line Feed LLO Local Lock Out MLA My Listen Address MTA My Talk Address PPC Parallel Poll Configure PPU Parallel Poll Unconfigure SC System Controller SDC Selected Device...

Страница 9: ...ery Digital488HS 32 is shipped with the following items Digital488HS 32 High Speed Digital I O Interface DigitalHS 901 Instruction Manual 167 0800 Accessory Kit which includes CA 1 Power Cable FU 1 25...

Страница 10: ...ist EN FULL iDAV POL iBUSY POL iEND POL iDATA POL SRQ EN SB1 SRQ EN SB2 SRQ EN EMPTY ist EN EMPTY oDAV POL oBUSY POL oEND POL oDATA POL TRIGGER POL CLR POL 8 7 6 5 4 3 2 1 OPEN 8 7 6 5 4 3 2 1 1 2 3 4...

Страница 11: ...ner Carefully remove the top cover Modify the parameters appropriate for your installation and carefully re assemble the interface using the reverse of the procedure described 2 2 2 1 Line Voltage Sel...

Страница 12: ...ment repeatedly blows fuses contact the factory 3 Open the fuse housing by pushing up on the tab on the bottom of the housing 4 Replace the fuse and close the housing Insert the fuse housing into the...

Страница 13: ...2 2 1 S2 1 SRQ EN Full Service Request Enable Service Request SRQ Enable causes the Digital488HS 32 to generate a service request on the IEEE 488 bus when iDAV transitions from the inactive not Full t...

Страница 14: ...ull Enabled S2 ist EN FULL Individual Status Message ist on Full Status 2 2 2 2 3 S2 3 iDAV POL Input Data Available Handshake Line The Input Data available handshake line is an input line sourced by...

Страница 15: ...2 2 2 5 S2 5 iEND POL Input End Control Line Polarity The iEND control line is latched into the ninth bit of the second byte input port This latched iEND signal directly drives the IEEE 488 EOI line...

Страница 16: ...data byte received by the IEEE 488 controller will be hF8 At power on iRESET Device Clear DCL or Selected Device Clear SDC the 16 bit digital input latches are forced to a Not Full condition Default s...

Страница 17: ...signal lines This active polarity is not switch selectable Each status bit can be polled by the IEEE 488 bus controller via serial polls The level of the signal is latched at the beginning of the ser...

Страница 18: ...eature Polarity Selection for Output Data oEND oTrigger oClear oDAV and oBusy Lines The digital output port contains 16 bits of TTL level outputs one END line oEND two handshake lines oDAV and oBusy f...

Страница 19: ...On Output Port Empty Selection 2 2 2 3 2 S3 2 ist EN EMPTY Individual Status Message True on Outut Port Empty Enable The Empty status can be sensed via parallel polls when the individual status messa...

Страница 20: ...utput port busy handshake line oBusy is an input sensed by the Digital488HS 32 It can be configured as active high or active low Factory default is active high OPEN 8 7 6 5 4 3 2 1 Active Low oBusy OP...

Страница 21: ...ort drivers are controlled by the output enable input OE In order to allow the digital output data to be presented to the output connector the OE input must be forced low The oEND output is always ena...

Страница 22: ...tive low or active high operation Default is active high Active Low oTrigger Active High oTrigger default OPEN 8 7 6 5 4 3 2 1 OPEN 8 7 6 5 4 3 2 1 S3 TRIGGER POL S3 TRIGGER POL Polarity Selection for...

Страница 23: ...6 5 4 3 2 1 OPEN 8 7 6 5 4 3 2 1 S3 CLR POL Active Low oClear Active High oClear default Polarity Selection for the oClear Line Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURC...

Страница 24: ...e oEND output is forced active 2 3 External Switches The Digital488HS 32 has one eight position switch accessible fron the rear panel This switch determines the unit s IEEE 488 bus address input and o...

Страница 25: ...s either 8 bit or 16 bit output port operation In 8 bit mode 8 bit data are transferred to the second byte port with the IEEE 488 bus EOI line driving the oEND output In 16 bit mode the first eight bi...

Страница 26: ...he external device can accept the data Normally the Digital488HS 32 uses the Not Ready For Data NRFD data lines for this purpose This allows the IEEE 488 bus to continue with other activity even thoug...

Страница 27: ...d NDAC Holdoff Enable Selection 2 3 4 IEEE 488 Address Selection Digital488HS 32 s IEEE 488 bus address is set by the switches labeled IEEE ADDRESS on the rear panel of the unit The address can be set...

Страница 28: ...out LLO Parallel Poll Disable PPD Take Control TCT 2 4 1 My Talk Address MTA When the Digital488HS 32 is addressed to talk it outputs any data available on the Digital Input Port If the interface has...

Страница 29: ...Listener Idle State 2 4 6 Serial Poll Enable SPE When Serial Poll Enabled SPE the Digital488HS 32 sets itself to respond to a serial poll with its serial poll status byte if addressed to talk When the...

Страница 30: ...bit line 2 See section 3 4 for more information 2 5 Front Panel Indicators Six indicator lights on the front panel of the Digital488HS 32 display the status of the interface The function of each indic...

Страница 31: ...ed the output data off when the output port is Not Empty FULL On when the Digital488HS 32 has accepted data on the Input Data Port from the external device Off when no input port data is pending that...

Страница 32: ...8 7 6 5 4 3 2 1 0 oEND Second Byte First Byte Output Port Organization First Byte Second Byte and oEND Bit Organization In 16 bit mode both the first byte and second byte ports are changed simultaneo...

Страница 33: ...s enabled OE does not affect the oEND control line The Output Enable control line OE places the output port buffers both first and second byte into tri state operation if left floating or forced activ...

Страница 34: ...ternal device has sensed the assertion of oDAV it must latch the data and then assert oBusy for at least 150 ns The external device must unassert oBusy when it is ready for more data First Byte Second...

Страница 35: ...nal device can accept the output port data If trigger must be synchronized with the data transfer it would be necessary to serial poll or parallel poll the Digital488HS 32 to determine if the data hav...

Страница 36: ...both the IEEE 488 bus talker and the IEEE 488 bus listener In fact the data on the bus can only transfer as fast as the slowest listener The Digital488HS 32 is capable of accepting bus data for transf...

Страница 37: ...line iBusy is active When sensed inactive all 17 bits of data can be presented to the input lines followed by a minimum delay of 50 ns after which iDAV can be forced active The leading transition of t...

Страница 38: ...ll up resistor causes the power on reset sequence when forced to a low state The polarity active level of this control line is not switch selectable iReset must be held active for at least 2 ms to ens...

Страница 39: ...DIO4 DIO3 DIO2 DIO1 Serial Poll Byte Bit Assignments These status bits include DIO1 FULL The input port is Full Data may be read from the input port DIO2 EMPTY The output port is Empty Data may be wr...

Страница 40: ...1 0 1 0 1 0 1 0 1 1 1 1 1 1 1 1 ist 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0 0 0 0 IEEE Bus Address Switch Status Parall...

Страница 41: ...evice can either be an instrument or a computer Before any information transfer can take place it is first necessary to specify which will do the talking send data and which devices will be allowed to...

Страница 42: ...information transfer is no faster than the rate at which the slowest note taker can keep up The instructor though may have a message for one particular student The instructor tells the rest of the cla...

Страница 43: ...ice 2 DMM Able to Talk and Listen Device 3 Printer Only Able to Listen Device 4 Frequency Counter Only Able to Talk Data Bus Data Byte Transfer Control General Interface Management IEEE 488 Bus Struct...

Страница 44: ...he Active Controller These commands include My Listen Address MLA My Talk Address MTA Talk Address Group TAG and Listen Address Group LAG 4 4 BUS MANAGEMENT LINES Five hardware lines on the GPIB are u...

Страница 45: ...or Identify EOI The EOI line is used to signal the last byte of a multibyte data transfer The device that is sending the data asserts EOI during the transfer of the last data byte The EOI signal is no...

Страница 46: ...to accept the information When NRFD and NDAC are in the proper state the Talker asserts DAV active low to indicate that the data on the bus is valid 4 5 2 Not Ready for Data NRFD This line is used by...

Страница 47: ...l and are active low 4 7 MULTILINE COMMANDS Multiline bus commands are sent by the Active Controller over the data bus with ATN asserted These commands include addressing commands for talk listen Unta...

Страница 48: ...7 5 Untalk UNT This command tells bus devices to Untalk The same as Unaddressed to Talk 5F 4 7 6 Local Lockout LLO Issuing the LLO command prevents manual control of the instrument s functions 11 4 7...

Страница 49: ...vices to begin simultaneously 08 4 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 4 7 13 Secon...

Страница 50: ...A power supply might SRQ if its output has current limited This is a powerful bus feature that removes the burden from the System Controller to periodically inquire Are you done yet Instead the Contr...

Страница 51: ...conditions on one data line by more than one device When SRQ is asserted the Controller under user s software conducts a Parallel Poll The Controller must then analyze the eight bits of data received...

Страница 52: ...9 30 UNL 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 UNT SCG SCG SCG SCG SCG SCG SCG SCG SCG SCG SCG SCG SCG SCG SCG SCG SCG SCG SCG SCG SCG SCG SCG SC...

Страница 53: ...T0 17 18 19 37 36 35 34 33 21 20 Digital Output Port Connector 1 19 20 37 5 volts Common iRESET SB2 SB1 1 8 9 16 Second Byte First Byte DIN15 DIN0 iBusy iDAV iEND 17 18 19 37 36 35 34 21 20 Digital In...

Страница 54: ...Output Tri state Output Tri state Output Tri state Output Tri state Output Tri state Output Tri state Output Tri state Output Output Input Vcc Ground Ground Ground Ground Ground Ground Ground Ground G...

Страница 55: ...Input Input Input Input Input Input Input Output Vcc Ground Ground Ground Ground Ground Ground Ground Ground Ground Ground Ground Ground Ground Ground Input Input Input Bit 0 Bit 1 Bit 2 Bit 3 Bit 4 B...

Страница 56: ...DAT to the parallel printer To begin construct this cable 1 19 20 37 34 OE 1 18 19 36 GND 19 GND 20 GND 21 GND 22 GND 23 GND 24 GND 25 GND 26 GND 27 GND 28 GND 29 GND 30 21 GND 22 GND 23 GND 24 GND 2...

Страница 57: ...igital488HS 32 to the printer with the fabricated cable Enter this simple program and print Sample Program IEEE 488 to Parallel Converter Using the IOtech Model Digital488HS 32 October 22 1991 Initial...

Страница 58: ...uipment Have surplus equipment taking up shelf space We ll give it a new home Learn more Visit us at artisantg com for more info on price quotes drivers technical specifications manuals and documentat...

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