National Instruments GPIB-130 User Manual

Contents

National Instruments GPIB-130 User Manual Manual pdf 27 page image

Appendix A Operation of the GPIB© National Instruments Corporation A-3 GPIB-130 User ManualNot Data Accepted (NDAC)NDAC indicates when a device has or has not accepted a message byte. The line is driven by alldevices when receiving commands and by Listeners when receiving data messages.Data Valid (DAV)DAV tells when the signals on the data lines are stable (valid) and can be accepted safely bydevices. The Controller drives DAV when sending commands and the Talker drives it whensending data messages.Interface Management LinesFive lines are used to manage the flow of information across the interface.Attention (ATN)The Controller drives ATN true when it uses the data lines to send commands and false when itallows a Talker to send data messages.Interface Clear (IFC)The System Controller drives the IFC line to initialize the bus and become CIC.Remote Enable (REN)The System Controller drives the REN line, which is used to place devices in remote or localprogram mode.Service Request (SRQ)Any device can drive the SRQ line to asynchronously request service from the Controller withthe SRQ line.End Or Identify (EOI)The EOI line has two purposes. The Talker uses the EOI line to mark the end of a messagestring. The Controller uses the EOI line to tell devices to identify their response in a parallelpoll.