Black Box IC026A-R2, IC026AE-R2 manual Ieee Data Transfers

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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. This bus hold-off will only occur until additional queues (more than 4) become available. Then the interface will resume accepting bus data.

5.3 IEEE Data Transfers

The following methods may be used by the IEEE controller when sending data to the interface converter:

5.3.1BLIND BUS DATA TRANSFERS

If the IEEE controller does not mind waiting an indefinite time for data space in the buffer to become available, the data can simply be sent to the interface converter. This is referred to as “blind data transfer,” because the IEEE controller is blind as to whether or not the interface converter is capable

of accepting data. In this case, the bus controller’s output data transfer will be held off by the interface converter if it is unable to buffer the data. It will resume accepting IEEE input data when memory becomes available. This type of control might be appropriate in a single-user environment.

To illustrate how this would appear, let’s assume the interface converter is connected to a serial device which will accept data at 1200 baud or 110 bytes per second. The IEEE bus controller is capable of sending data to the interface converter at a rate of 5000 bytes per second. The data would be transferred on the bus at 5000 characters per second for slightly over six seconds, filling over 31,000 locations. At that time, the IEEE input would hold off additional data transfers until 128 characters are sent out the serial port at rate of 110 characters per second. This 110 cps would then become the average bus data acceptance rate of the interface converter.

If the controller is set to detect a data time-out error, then it will do so if the interface converter holds off IEEE input data transfers for too long. The error can be used to alert the operator to the problem, such as a printer out of paper, so that it can be corrected. If the controller then restarts transmission exactly where it left off, no data will be lost.

If data is requested by the controller and no serial input data is available in the interface converter, the bus will hang until serial data is received. If no serial data is received, it will hang forever until the controller times out.

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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 Specifications GeneralIntroduction DescriptionAbbreviations Inspection ConfigurationGetting Started 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 Switch SW2 Selecting the Serial Terminator Selecting Terminator SubstitutionSelecting the Mode Switch SW3 Selecting the Ieee Bus Terminator10. Switch SW2 Selecting the Mode Selecting the Ieee AddressFeature Selections Serial Interface 15. Selecting RS-232 or RS-422 Signal Levels Clear To Send-Input-Pin RxD Receive Data-Input-PinTxD Transmit Data-Output-Pin Request To Send-Output-Pin+RxD Receive Data Plus-Input-Pin Vtest Test Voltage-Output-PinGnd Ground-Pin +TxD Transmit Data Plus-Output-PinRTS CTS General DSR RTS CTSGetting Started Controller Operation Controller-Mode Serial to Ieee OperationSerial and Ieee Terminator Substitution Talk-Back Features Ieee Address SelectionSwitch SW1 Enabling or Disabling Talk-Back on Terminator Switch SW2 Enabling or Disabling Talk-Back on Timeout 7470A SP1PA1000,1000PDPA1000,6000PUSP0Plotter 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 Serial-Poll Status-Byte Register DIO8 Ieee Input Buffer not EmptySerial Input Buffer not Empty RsvNot Defined-Always Ieee Input Buffer FullUse of Serial and Bus Terminators Ieee 488 Bus ImplementationUntalk UNT SW3 View for Ieee Address Selection History Ieee 488 PrimerGeneral Structure RS-232↔IEEE 488 Interface Converter Send It to My Address DMMBus Management Lines Handshake Lines Data Valid DAVMultiline Commands Data LinesTalk Address Group TAG More on Service Requests Serial Poll Theory of Operation Address Device Part Number FunctionBoard Layout Component Layout of the Interface Converter’s MotherboardRED BLK Appendix A. Sample Dumb-Terminal Program CLSMultiline Messages SOHHow To Read the Chart Ascii CharacterIndex DIO1 DIO2 DIO3Index SW1 Copyright 1998. Black Box Corporation. All rights reserved
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