National Instruments PC-DIO-24 User Manual

Contents

National Instruments PC-DIO-24 User Manual Manual pdf 29 page image

© National Instruments Corporation 3-1 PC-DIO-24 User ManualChapter 3Theory of OperationThis chapter contains a functional overview of the PC-DIO-24 board and explains the operationof each functional unit making up the PC-DIO-24.The block diagram in Figure 3-1 illustrates the key functional components of the PC-DIO-24board.I/O ConnectorInterruptControlCircuitry82C55APPIPC I/OChannelControlCircuitryAddressDecoderBusTransceiversPAPBPC/8/8/8PC3PC0+5 VPC I/O Channel1 A FuseFigure 3-1. PC-DIO-24 Block DiagramThe PC I/O Channel consists of an address bus, a data bus, interrupt lines, and several controland support signals. Control and data transfers to the system microprocessor are asynchronous.