Black Box IC026AE-R2, IC026A-R2 manual Controlled BUS Data Transfers

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CHAPTER 5: Peripheral Operation

5.3.2CONTROLLED 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.

When serial-polled, the interface converter provides eight bits of status information to the controller. The most significant bit (DIO8) of the interface converter’s serial poll byte is set to a logic “1” when the IEEE input buffer is NOT EMPTY. The term NOT EMPTY is used to signify that not all of the previous data sent to the interface has been transmitted to the serial device. If it is NOT EMPTY, the controller may avoid sending any more data to the interface converter. If this bit is a logic “0,” then the serial device has accepted all previous data and the IEEE controller may send more.

Another bit (DIO4) of the Serial Poll byte is used to indicate additional information concerning the IEEE input buffer. This bit is set to a logic “1” when there is 1280 or less locations in the buffer for data. It is cleared, set to a logic “0”, when there is greater than 1280 locations available. This bit is referred to as the IEEE input buffer FULL bit.

When serial data is received, DIO5 of the Serial Poll byte is set to “1”, to indicate to the IEEE controller that the serial input buffer is NOT EMPTY. If this bit is set, it indicates that at least one character is available in the serial input buffer to be read by the IEEE controller. Once all of the serial input data is read by the IEEE controller this bit is reset.

The interface converter can generate a request for service on the bus when it receives the last serial terminator. To enable this feature, the Peripheral SRQ switch, located on the internal switch bank of SW1, must be enabled. When SRQ is enabled, the interface converter will assert the IEEE bus SRQ line and set serial poll status bits DIO7 and DIO3 when the last serial terminator is detected. The IEEE controller must perform a serial poll on the interface to clear the SRQ. If the Peripheral SRQ switch is in the disabled position, there will not be any indication in the serial-poll status byte that a serial terminator has been received.

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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 Serial Interface SpecificationsIEEE-488 Interface General SpecificationsDescription IntroductionAbbreviations Serial Port ConfigurationGetting Started InspectionSW3 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 Request To Send-Output-Pin RxD Receive Data-Input-PinTxD Transmit Data-Output-Pin Clear To Send-Input-Pin+TxD Transmit Data Plus-Output-Pin Vtest Test Voltage-Output-PinGnd Ground-Pin +RxD Receive Data Plus-Input-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 Serial and Ieee Input Buffers Peripheral OperationPeripheral-Mode Operation Ieee Data Transfers Controlled BUS Data Transfers DIO8 Ieee Input Buffer not Empty Serial-Poll Status-Byte RegisterIeee Input Buffer Full RsvNot Defined-Always Serial Input Buffer not EmptyIeee 488 Bus Implementation Use of Serial and Bus TerminatorsUntalk UNT SW3 View for Ieee Address Selection General Structure Ieee 488 PrimerHistory 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
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