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National Instruments GPIB-140B User Manual Download Page 15

Figure 11. DIP Switch Setting for Immediate PPR Mode

OFF

 = Not used to set Parallel Poll Response (PPR) mode

PARALLEL POLL IMMEDIATE

HS488 ENABLED
BUFFERED TRANSFER

Theory of Operation

This section describes how the GPIB extender circuitry operates.

This section assumes that you are familiar with GPIB. If you are a first-time user or if you
would like to review the basics about GPIB, refer to 

GPIB Basics

 on page 16.

The following figure shows the five layers of a GPIB extender. To form a complete link, you
can connect each layer to the corresponding layer of another extender at the remote side.

Figure 12. GPIB Extender Block Diagram

Message Interpreter

Layer

Message Interpreter

Layer

Packet Translation

Layer

Packet Translation

Layer

Link Management

Layer

Link Management

Layer

Parallel-to-Serial

Conversion Layer

Physical Layer

GPIB BUS #2

GPIB BUS #1

GPIB EXTENDER

GPIB EXTENDER

Transmission

Medium

Physical Layer

Parallel-to-Serial

Conversion Layer

GPIB-140B User Manual

  | 

© National Instruments Corporation

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15

Summary of Contents for GPIB-140B

Page 1: ...B 140B Description 4 GPIB 140B Dimensions 5 Grounding the GPIB 140B 6 LED Indicators 8 DIP Switches 8 Hardware Connections 9 Connecting the Cables 9 Connecting the External Power Supply 10 Verifying the Connection 10 Hardware Configuration 11 Data Transfer Modes 11 HS488 Mode 12 Parallel Poll Response Modes 13 Theory of Operation 15 GPIB Basics 16 Introduction to HS488 21 Multiline Interface Messa...

Page 2: ... what ships with the GPIB 140B ensure that the adapter provides 9 V DC to 15 V DC and has appropriate safety certification marks for country of use Optional Equipment The following table lists some cables available for the GPIB 140B For a complete list of GPIB accessories and ordering information refer to the pricing section of the Fiber Optic Cable and GPIB Cable product pages at ni com Note The ...

Page 3: ...ouching a grounded object Touch the antistatic package to a metal part of your computer chassis before removing the device from the package Remove the device from the package and inspect it for loose components or any other signs of damage Notify NI if the device appears damaged in any way Do not install a damaged device Store the device in the antistatic package when the device is not in use Hard...

Page 4: ...ms in a functionally transparent manner The two bus systems are physically separate as shown in the following figure Figure 1 Typical Extension System Physical Configuration Printer Listener GPIB Cable Computer System Controller Talker and Listener GPIB Cable Multi Mode Fiber Optic Cable Signal Generator Listener Unit Under Test Multimeter Talker and Listener GPIB 140B GPIB 140B GPIB Cable The dev...

Page 5: ...mum data transfer rate over the extension is greater than 2 8 MBytes s The GPIB extenders use a buffered transfer technique with a serial extension bus which maximizes performance and minimizes the cabling cost Furthermore the extender does not affect the transfer rate between devices on the same side of the extension The GPIB extender can also check for errors to make sure that the data transmitt...

Page 6: ... IMMEDIATE GPIB 140B FIBER OPTIC GPIB EXTENDER HS488 ENABLED BUFFERED TRANSFER ON OFF 28 80 mm 1 134 in RECEIVE TRANSMIT INPUT 9 to 15 V 3 W MAX Grounding the GPIB 140B You must connect the GPIB 140B grounding terminal to the grounding electrode system of the facility Note For more information about ground connections visit ni com r emcground 6 ni com GPIB 140B User Manual ...

Page 7: ...B EXTENDER HS4 88 EN ABL ED BU FF ER ED TR ANSF ER ON OFF 1 Attach the ring lug to the wire 2 Remove the grounding screw from the grounding terminal on the side panel of the product 3 Fasten the ring lug to the grounding terminal 4 Tighten the grounding screw to 1 3 N m 11 5 in lb of torque 5 Attach the other end of the wire to the chassis safety ground using a method that is appropriate for your ...

Page 8: ...e Off The fiber optic cable is defective or disconnected or the remote GPIB 140B is turned off STATUS Green Flashing 10 Hz Activity is present on the GPIB bus Red Solid The fiber optic cable is either defective or disconnected or the GPIB 140B is turned off Red Flashing 10 Hz The GPIB 140B is receiving corrupted data and starts re transmission The red LED turns off after 50 ms and flashes green wh...

Page 9: ...tic cable Do not use with single mode cable Complete the following steps to connect a multi mode fiber optic cable to both GPIB extenders 1 Make sure that each GPIB 140B extender is powered off 2 Connect the two connectors on each end of the fiber optic cable to your GPIB extenders as follows a As shown in the following figure align the connector marked T transmit with the connector labeled TRANSM...

Page 10: ... the POWER LED lights green If the LED does not light green make sure that the supply voltage is in the acceptable range The LINK LED lights green when multiple GPIB extenders are properly connected and turned on Note Refer to LED Indicators on page 8 for detailed information about the behavior of each LED Verifying the Connection Each GPIB extender has a self test that determines whether the GPIB...

Page 11: ...he fiber optic cable connectors does not solve the problem continue to the next step 3 Repeat steps 4 and 5 using a different fiber optic cable If the problem persists you might need to replace your GPIB extender For more information contact NI for support Note Refer to LED Indicators on page 8 for detailed information about the behavior of each LED Hardware Configuration This section describes ho...

Page 12: ...tocol Setting the Data Transfer Mode The two GPIB extenders in your extension system must use the same data transfer mode To use buffered mode set the BUFFERED TRANSFER DIP switch to the ON position as shown in the following figure To use unbuffered mode set this switch to the OFF position Figure 9 DIP Switch Setting for Buffered Mode OFF PARALLEL POLL IMMEDIATE HS488 ENABLED BUFFERED TRANSFER Not...

Page 13: ...lel poll within 200 ns after the Controller In Charge CIC asserts the Identify IDY message Attention ATN and End or Identify EOI The CIC waits at least 2 µs before reading the Parallel Poll Response PPR In many cases a remote device on an extended system cannot respond to parallel polls this quickly because of cable propagation delays To solve this problem use one of the following two solutions in...

Page 14: ... asserts IDY the local extender sends the IDY message to the remote bus and the response is returned as fast as propagation delays permit Your application must allow enough time to receive the response Latched PPR Mode In latched PPR mode the GPIB extenders use an internal PPR data register When a Controller on the local system asserts IDY the local extender sends the contents of the PPR data regi...

Page 15: ...n page 16 The following figure shows the five layers of a GPIB extender To form a complete link you can connect each layer to the corresponding layer of another extender at the remote side Figure 12 GPIB Extender Block Diagram Message Interpreter Layer Message Interpreter Layer Packet Translation Layer Packet Translation Layer Link Management Layer Link Management Layer Parallel to Serial Conversi...

Page 16: ...r if it detects a transmission error then it re transmits the packets Parallel to Serial Conversion Layer The Parallel to Serial Conversion Layer accepts packets from the Link Management Layer converts them into serial data and sends the data to the Physical Layer It also extracts serial bits from the Physical Layer reconstructs them back into packets and sends them to the Link Management Layer Ph...

Page 17: ...ware installed it can function as a Talker Listener and Controller The GPIB is like a typical computer bus except that the typical computer has circuit cards interconnected via a backplane bus whereas the GPIB has standalone devices interconnected via a cable bus The role of the GPIB Controller is similar to the role of the CPU of a computer but a better analogy is to the switching center of a cit...

Page 18: ...tween devices This process is a three wire interlocked handshake and it guarantees that devices send and receive message bytes on the data lines without transmission error The following table summarizes the GPIB handshake lines Table 3 GPIB Handshake Lines Line Description NRFD not ready for data Listening device is ready not ready to receive a message byte Also used by the Talker to signal high s...

Page 19: ... assembly consisting of a shielded 24 conductor cable with both a plug and receptacle connector at each end as shown in the following figure Figure 13 GPIB Connector and Signal Assignments 13 14 15 16 17 18 19 20 21 22 23 24 1 2 3 4 5 6 7 8 9 10 11 12 DIO5 DIO6 DIO7 DIO8 REN GND TW PAIR W DAV GND TW PAIR W NRFD GND TW PAIR W NDAC GND TW PAIR W IFC GND TW PAIR W SRQ GND TW PAIR W ATN SIGNAL GROUND ...

Page 20: ...GPIB was designed for you must limit the number of devices on the bus and the physical distance between devices The following restrictions are typical A maximum separation of 4 m between any two devices and an average separation of 2 m over the entire bus A maximum total cable length of 20 m A maximum of 15 devices connected to each bus with at least two thirds powered on For high speed operation ...

Page 21: ... rate Compatibility with IEEE 488 Devices HS488 is a superset of the IEEE 488 standard thus you can mix IEEE 488 1 IEEE 488 2 and HS488 devices in the same system When connected to an HS488 device the Controller does not need to be capable of HS488 non interlocked transfers While ATN is asserted the Controller sources multiline messages to HS488 devices just as it sources multiline messages to any...

Page 22: ...ices must have a buffer of at least 3 bytes to store received data HS488 devices must implement the Configuration CF interface function At system power on the Controller uses previously undefined multiline messages to configure HS488 devices The CF function enables devices to interpret these multiline messages Sequence of Events in Data Transfers The following figure shows a typical IEEE 488 1 dat...

Page 23: ...d handshake First byte transferred using 488 1 handshake T13 T1 T14 ATN DIO18 composite DAV NFRD NDAC 1 The Controller addresses devices and becomes Standby Controller by unasserting ATN 2 The Listener asserts NDAC and NRFD 3 The Listener unasserts NRFD as it becomes ready to accept a byte 4 After allowing time for the Listener to detect NRFD unasserted the Talker indicates that it is HS488 capabl...

Page 24: ... but the Listener is not Figure 18 HS488 Capable Talker Low going transition on NRFD indicates that not all receiving devices are high speed capable High speed capable signal ATN DIO18 composite DAV NFRD NDAC T1 Steps 1 6 in the sequence are identical to steps 1 6 in the previous procedure Case 1 Talker and Listener are HS488 Capable on page 23 The Listener ignores the HSC message from the Talker ...

Page 25: ... The Secondary Command has the bit pattern 6n hex where n is the meters of cable in the system The SCG includes CFG1 CFG15 in the Multiline Interface Messages section Multiline Interface Messages This section lists the multiline interface messages and describes the mnemonics and messages that correspond to the interface functions The multiline interface messages are commands defined by the IEEE 48...

Page 26: ...F 2A 42 MLA10 0B 11 VT 2B 43 MLA11 0C 12 FF 2C 44 MLA12 0D 13 CR 2D 45 MLA13 0E 14 SO 2E 46 MLA14 0F 15 SI 2F 47 MLA15 10 16 DLE 30 48 0 MLA16 11 17 DC1 LLO 31 49 1 MLA17 12 18 DC2 32 50 2 MLA18 13 19 DC3 33 51 3 MLA19 14 20 DC4 DCL 34 52 4 MLA20 15 21 NAK PPU 35 53 5 MLA21 16 22 SYN 36 54 6 MLA22 17 23 ETB 37 55 7 MLA23 18 24 CAN SPE 38 56 8 MLA24 19 25 EM SPD 39 57 9 MLA25 1A 26 SUB 3A 58 MLA26 ...

Page 27: ...TA6 66 102 f MSA6 PPE CFG6 47 71 G MTA7 67 103 g MSA7 PPE CFG7 48 72 H MTA8 68 104 h MSA8 PPE CFG8 49 73 I MTA9 69 105 i MSA9 PPE CFG9 4A 74 J MTA10 6A 106 j MSA10 PPE CFG10 4B 75 K MTA11 6B 107 k MSA11 PPE CFG11 4C 76 L MTA12 6C 108 l MSA12 PPE CFG12 4D 77 M MTA13 6D 109 m MSA13 PPE CFG13 4E 78 N MTA14 6E 110 n MSA14 PPE CFG14 4F 79 O MTA15 6F 111 o MSA15 PPE CFG15 50 80 P MTA16 70 112 p MSA16 PP...

Page 28: ... _ UNT 7F 127 DEL Multiline Interface Message Definitions CFE Configuration Enable PPD Parallel Poll Disable CFG Configure PPE Parallel Poll Enable DCL Device Clear PPU Parallel Poll Unconfigure GET Group Execute Trigger SDC Selected Device Clear GTL Go To Local SPD Serial Poll Disable LLO Local Lockout SPE Serial Poll Enable MLA My Listen Address TCT Take Control MSA My Secondary Address UNL Unli...

Page 29: ...rces including documentation downloads and troubleshooting and application development self help such as tutorials and examples Visit ni com services to learn about NI service offerings such as calibration options repair and replacement Visit ni com register to register your NI product Product registration facilitates technical support and ensures that you receive important information updates fro...

Page 30: ...EULAs and third party legal notices in the readme file for your NI product Refer to the Export Compliance Information at ni com legal export compliance for the NI global trade compliance policy and how to obtain relevant HTS codes ECCNs and other import export data NI MAKES NO EXPRESS OR IMPLIED WARRANTIES AS TO THE ACCURACY OF THE INFORMATION CONTAINED HEREIN AND SHALL NOT BE LIABLE FOR ANY ERROR...

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