IEEE 488 Introduction
PSI BOX Reference
of the participating devices.
DAV Data Valid.
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The DAV line indicates that the data on the data lines is
good data. The DAV is controlled by the device that is putting
the data on the data bus. The DAV line is monitored by all the
devices that are accepting data from the data bus. The DAV line
is false when the data on the data bus is invalid and is true
when the data bus contains valid data.
NRFD Not Ready For Data.
________________________
The NRFD line indicates the condition of readiness of
devices to accept data. The NRFD line is monitored by the
device that puts the data on the data bus. It is driven by all the
devices that are accepting data from the data bus.
The NRFD line is false when the all these devices are ready for
data and true when one or more of them is not ready for data.
NDAC Not Data Accepted.
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The NDAC line indicates acceptance of data by the
devices.
The NDAC line is monitored by the device that puts the data on
the data bus. It is driven by all the devices that are accepting
data from the data bus. When NDAC is true, one or more of
the listening devices have not accepted the data.
The Management Signals.
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The 5 management signals are ATN, IFC, SRQ REN and
EOI. These five signals are used to manage an orderly flow of
information across the bus.
The ATN and IFC lines are used by all IEEE bus devices. The
remaining three, REN, SRQ and EOI, may or may not be used
Chapter 2
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