Black Box IC026AE-R2, IC026A-R2 manual Serial Poll

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CHAPTER 6: IEEE 488 Primer

6.8.1SERIAL 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. This Serial Polling sequence, and any resulting action, is under control of the software designer.

6.8.2PARALLEL POLL

The Parallel Poll is another way the Controller can determine which device requested service. It provides the who but not necessarily the why. When bus devices are configured for Parallel Poll, they are assigned one bit on the data bus for their response. By using the Status bit, the logic level of the response can be programmed to allow logical OR/AND 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 to determine the source of the request. Once the source is determined, a Serial Poll might be used to determine the why.

Of the two polling types, the Serial Poll is the most popular due to its ability to determine the who and why. In addition, most devices support Serial Poll only.

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Contents RS-232↔IEEE Interface Converter RS-232↔IEEE 488 Interface Converter Trademarks Used in this Manual RS-232↔IEEE 488 Interface Converter NOM Statement RS-232↔IEEE 488 Interface Converter Contents RS-232↔IEEE 488 Interface Converter Contents IEEE-488 Interface SpecificationsSerial Interface General SpecificationsDescription IntroductionAbbreviations Getting Started ConfigurationInspection Serial PortSW3 Serial Port Settings Switch SW1 Selecting the Serial Baud Rate Switch SW1 Selecting the Serial Word Length Data Bits Switch SW2 Selecting the Serial Parity Switch SW1 Selecting the Serial Handshake Selecting Terminator Substitution Switch SW2 Selecting the Serial TerminatorSwitch SW3 Selecting the Ieee Bus Terminator Selecting the ModeSelecting the Ieee Address 10. Switch SW2 Selecting the ModeFeature Selections Serial Interface 15. Selecting RS-232 or RS-422 Signal Levels TxD Transmit Data-Output-Pin RxD Receive Data-Input-PinClear To Send-Input-Pin Request To Send-Output-PinGnd Ground-Pin Vtest Test Voltage-Output-Pin+RxD Receive Data Plus-Input-Pin +TxD Transmit Data Plus-Output-PinRTS CTS DSR RTS CTS GeneralGetting Started Controller-Mode Serial to Ieee Operation Controller OperationSerial and Ieee Terminator Substitution Ieee Address Selection Talk-Back FeaturesSwitch SW1 Enabling or Disabling Talk-Back on Terminator Switch SW2 Enabling or Disabling Talk-Back on Timeout SP1PA1000,1000PDPA1000,6000PUSP0 7470APlotter Applications A PC-Based Graphics System SW3 MacPlot Configuration Screen Setting the Internal DIP Shorting Jumper for RS-422 SW3 Printer Applications Peripheral-Mode Operation Peripheral OperationSerial and Ieee Input Buffers Ieee Data Transfers Controlled BUS Data Transfers DIO8 Ieee Input Buffer not Empty Serial-Poll Status-Byte RegisterNot Defined-Always RsvSerial Input Buffer not Empty Ieee Input Buffer FullIeee 488 Bus Implementation Use of Serial and Bus TerminatorsUntalk UNT SW3 View for Ieee Address Selection History Ieee 488 PrimerGeneral Structure RS-232↔IEEE 488 Interface Converter DMM Send It to My AddressBus Management Lines Data Valid DAV Handshake LinesData Lines Multiline CommandsTalk Address Group TAG More on Service Requests Serial Poll Address Device Part Number Function Theory of OperationComponent Layout of the Interface Converter’s Motherboard Board LayoutRED BLK CLS Appendix A. Sample Dumb-Terminal ProgramSOH Multiline MessagesAscii Character How To Read the ChartDIO1 DIO2 DIO3 IndexIndex SW1 Copyright 1998. Black Box Corporation. All rights reserved