D-6
IEEE-488 Bus Overview
Once all NDAC and NRFD are properly set, the source sets DAV low, indicating to accept-
ing devices that the byte on the data lines is now valid. NRFD will then go low, and NDAC will
go high once all devices have accepted the data. Each device will release NDAC at its own rate,
but NDAC will not be released to go high until all devices have accepted the data byte.
The sequence just described is used to transfer both data, talk and listen addresses, as well as
multiline commands. The state of the ATN line determines whether the data bus contains data,
addresses or commands as described in the following paragraph.
Bus commands
The instrument may be given a number of special bus commands through the IEEE-488
interface. This section brie
fl
y describes the purpose of the bus commands which are grouped
into the following four categories.
1.
Uniline commands
—
Sent by setting the associated bus lines true. For example, to
assert REN (Remote Enable), the REN line would be set low (true).
2.
Multiline commands
—
General bus commands which are sent over the data lines with
the ATN line true (low).
3.
Common commands
—
Commands that are common to all devices on the bus; sent
with ATN high (false).
4.
SCPI commands
—
Commands that are particular to each device on the bus; sent with
ATN (false).
These bus commands and their general purpose are summarized in Table D-1.
DATA
DAV
SOURCE
SOURCE
VALID
ALL READY
ACCEPTOR
NRFD
NDAC
ALL ACCEPTED
ACCEPTOR
Figure D-2
IEEE-488 handshake
sequence
Summary of Contents for 6430
Page 26: ......
Page 32: ......
Page 78: ...2 14 Connections ...
Page 98: ...3 20 Basic Source Measure Operation ...
Page 138: ...5 30 Source Measure Concepts ...
Page 156: ...6 18 Range Digits Speed and Filters ...
Page 168: ...7 12 Relative and Math ...
Page 176: ...8 8 Data Store ...
Page 202: ...9 26 Sweep Operation ...
Page 248: ...11 22 Limit Testing ...
Page 310: ...16 6 SCPI Signal Oriented Measurement Commands ...
Page 418: ...17 108 SCPI Command Reference ...
Page 450: ...18 32 Performance Verification ...
Page 477: ...A Specifications ...
Page 489: ...B StatusandErrorMessages ...
Page 498: ...B 10 Status and Error Messages ...
Page 499: ...C DataFlow ...
Page 503: ...D IEEE 488BusOverview ...
Page 518: ...D 16 IEEE 488 Bus Overview ...
Page 519: ...E IEEE 488andSCPI ConformanceInformation ...
Page 523: ...F MeasurementConsiderations ...
Page 539: ...G GPIB488 1Protocol ...
Page 557: ......