National Instruments PC-DIO-24 User Manual

Contents

National Instruments PC-DIO-24 User Manual Manual pdf 25 page image

Configuration and Installation Chapter 2PC-DIO-24 User Manual 2-8 © National Instruments CorporationTiming SpecificationsThis section lists the timing specifications for handshaking with the PC-DIO-24. Thehandshaking lines STB* and IBF synchronize input transfers. The handshaking lines OBF* andACK* synchronize output transfers.The following signals are used in the timing diagrams on the subsequent pages.Name SignalDirectionDescriptionSTB* Input Strobe Input—A low signal on this handshaking line loads data into the inputlatch.IBF Output Input Buffer Full—A high signal on this handshaking line indicates that datahas been loaded into the input latch. This is an input acknowledge signal.ACK* Input Acknowledge Input—A low signal on this handshaking line indicates thatthe data written from the selected port has been accepted. This signal is aresponse from the external device that it has received the data from thePC-DIO-24.OBF* Output Output Buffer Full—A low signal on this handshaking line indicates thatdata has been written from the selected port.INTR Output Interrupt Request—This signal becomes high when the 82C55A isrequesting service during a data transfer. The appropriate interrupt enablebits must be set to generate this signal.RD* Internal Read Signal—This signal is the read signal generated from the control linesof the PC.WR* Internal Write Signal—This signal is the write signal generated from the control linesof the PC.DATA Bidirectional Data Lines at the Selected Port—This signal indicates when the data on thedata lines at a selected port is or should be available.