SECTION 4
IEEE-488
Reference
Programming Example - Type in the following state-
ments toplacetheinstrumentintheone-shot GETtrigger
mode.
REMOT!? 722
oT.mwT 7z;‘T3x”
Now trigger a reading by sending GET with the follow-
ing statement:
TRIGGER 722
This sends IEEE-488 co
mmandsUNTLJNLLISTEN22
GET. When the RlXCJRN key is pressed, a reading con-
version occurs. (The command TRIGGER 7 just sends
GET. AU listeners are triggered when the RETURN key is
pressed.)
4.3.8 SPE, SPD (Serial Polling)
The serial polling sequence is used to obtain the Model
486/487 serial poll byte. The serial poll byte contains im-
portant information about internal functions, as de
sa’iied in paragraph 4.211. Generally, the serial polling
sequence is used by the controller to determine which of
several instrumenk has requested service with the SRQ
line. However, the serial polling sequence may be per-
formed at any time to obtain the status byte from the
Model 486/487.
Programming Example - The SPOLL statement auto-
maticdy performs the serial poll sequence. To demon-
strate serial polling, enter in the following statements
into the computer:
S=SPOLL (722)
PRINT “SPOLL BYIE =“;S
After the first statement, the controller conducts the se-
rial polling sequence, After the second statement is exe-
cuted, the decimal value of the serial poll byte is dis-
played on the controller CRT.
4.4 IEEE-488 BUS CONNECTIONS
The Model 486/487 is intended to be connected to the
IEEE-488 Bus through a cable equipped with standard
4-46
IEEE-&3 connectors, an example of which is shown in
Figure 49 The connector is intended to be stacked to al-
low a number parallel connections at one instrument.
Two screws are located on each connector to ensure that
connections remain secure. Current standards call for
metric threads, which are identified with dark colored
screws. Earlier versions had different sbews, which were
silvercolored. Donotattempttousethesetypeofconnec-
tars on the instrument, which is designed for metric
threads.
1 Fixwed-9.
IEEE-488 Connector
A typical connecting scheme for a multi-unit test system
isshowninFigure410.Althoughanynumberofconnec-
tars could theoretically be stacked on one instnmwnt, it is
recommended that you stack no more than three connec-
tors on any one unit to avoid possible mechanical dam-
age.
NOTE
In order to
minimize interference caused by
electromagnetic radiation, it is recommended
that only shielded IEEE-488 cables be used.
The Models 7007-I and 7007-Z shielded
IEEE-488 cables are available from Keithley.
Connect the Model 486/487 to the IEEE-488 Bus as fol-
lows:
1. Line up the cable connector with the connector lo-
cated
on
the rear panel of the Source Measure Unit.
The connector is designed so that it will fit only one
way. Figure 411 shows the location of the IEEE-488
connector on the instrument.
2. Tighten the screws securely, but do not overtighten
them.
3. Add additional connectors from other insbuments,
as required.
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