Keithley 708A Instruction Manual Download

Page: 59 / 167

Operation

4-10

3. To re-initialize the loop, make sure master/slave cables

are secure, and cycle power of all units.

4.6.5 IEEE-488 bus address

The Model 708A communicates over the IEEE-488 bus
through the rear panel connection shown in Figure 4-12.
When connected to a bus controller, instrument operating
modes can be programmed. Note that IEEE-488 common is
always grounded.

Two rotary switches on the rear panel of the Model 708A are
used to set the IEEE-488 address. One switch is used to set
each digit of the address. The primary address of the Model
708A is factory set to 18, but it may be set to any value be-
tween 0 and 30 (between 30 and 60 for a master unit) as long
as address conflicts with other instruments or the bus control-
ler are avoided. Actual master unit addresses for program-
ming will be 30 less than the address set on the Model 708A.

To check the present primary address, look on the rear panel
of the Model 708A. If the value is above 30, the actual IEEE-
488 address will be 30 less. To change the address, perform
the following procedure:

1. Power down the unit (stand-alone) or units (master/

slave).

2. Change the position of the rotary switches (Figure 4-12)

to the new address.

NOTE

Each device on the bus must have a unique
primary address. Failure to observe this
precaution could result in erratic bus oper-
ation. In a master/slave configuration, only
the master Model 708A Switching System
IEEE-488 address will be used. The IEEE-
488 address is updated only at power-up.

Section 5 contains detailed information on operating the
Model 708A over the IEEE-488 bus.

IEEE-488

ADDRESS

IEEE-488 INTERFACE

Figure 4-12

IEEE-488 bus connector and rotary selection switches

4.6.6 Hardware relay settling times

The card specification relay settling time is the time needed
for the relays to actuate or release (including contact bounce
time) and pass a clean signal. Since this specification is card
dependent, the Model 708A must identify on power-up
which cards are installed to determine the longest relay set-
tling time in the system (stand-alone or master/slave). This
value is not user-modified, but the total settling time for a
switching operation can be lengthened by using the pro-
grammed settling time, as explained in paragraph 4.7.1.

To view the relay (hardware) settling time of the system, use
the U6 — status command (paragraph 5.9.20).

See paragraph 4.8 for a discussion of settling times and
triggers.

4.6.7 Self-test

The self-test program is used to check ROM, RAM, and
allow inspection of the front panel LED indicators. This test
is also part of the power-up sequence. If you want to run the
test without cycling power, use the J0 — self test command
(paragraph 5.9.9).

If there is an error in ROM or RAM, the ERR LED is lit until
a keypress or bus operation. See Section 7 for troubleshoot-
ing procedures.

For master/slave configurations, all units are tested simulta-
neously, so you might have to run the test more than once to
inspect all LED indicators. Program 99 will turn on all
LEDs. This is done by setting the IEEE address switch to 99
and cycling power.

4.6.8 Factory defaults

A command can be used to return the Model 708A to the
factory default conditions listed in Table 4-2. To initiate this
action, use the R0 — restore defaults command (paragraph
5.9.17).

In master/slave configurations, all units return to factory
defaults when this is sent to the master unit.

4.7

Selecting switching parameters

The Model 708A has three switching parameters that are
user-modified: the programmed settling time, make-before-
break rows, and break-before-make rows. The values of
these parameters are in effect for all relay switching until
they are changed. To modify the parameter, use the appropri-
ate command.

Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com