Black Box IC026A-R2, IC026AE-R2 manual Theory of Operation, Address Device Part Number Function

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RS-232↔IEEE 488 INTERFACE CONVERTER

7.Theory of Operation and Board Layout

7.1Theory of Operation

The heart of the interface converter is a 6809 microprocessor (U101) supported by 8K bytes of firmware EPROM [U102 (2764)] and 32K bytes of static RAM [U103 (58256)]. A Versatile Interface Adapter [U104 (65B22)] is used to generate real-time interrupts for the firmware operating system.

The front-panel annunciators are also driven by U104 through an inverter [U113 (74LS04)]. The IEEE 488 bus interface is accomplished by a TMS9914A [U106] controller with drivers U107 and U108. The serial interface is provided by the UART [6551 (U105)]. If RS-232 levels are chosen, they are provided by the RS-232 transceiver (U209). If RS-422 levels are selected, the differential driver [26LS30 (U207)] and receiver [26LS33 (U208)] are used.

The internal DIP switches [SW1, SW2, and SW3] are read via 74HCT244 tri-state buffers [U201, U202 and U203]. Power is supplied by an external unregulated 9-volt wallmount supply. Regulation to the required +5 volts is provided by U206 [7805].

Decoding of the microprocessor address space is accomplished with a Programmable Logic Array [U110 (16L8)]. The Memory space allocation is:

Address	Device	Part Number	Function
$0000-$7FFF	U103	58258	Static RAM
$A000-$A007	U106	9914A	IEEE Controller
$A800-$A807	U105	6551	UART
$B000-$B00F	U104	65B22	VIA
$B800	U201	74HCT244	SW1 (S201)
$B801	U202	74HCT244	SW2 (S202)
$B802	U203	74HCT244	SW3 (S203)
$E000-$FFFF	U102	2764	Programmed EPROM

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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 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 Serial and Ieee Input Buffers Peripheral OperationPeripheral-Mode Operation 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 General Structure Ieee 488 PrimerHistory 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