Ieee-488 Status Indicators - Keithley 486 Instruction Manual

SECTION 4
IEEE-488 Reference
The trigger stimulus that causes the trigger overrun is ig-
nored but denoted in the Ul error status word and by the
following message that is briefly displayed:
TRG OVERUN
Cal Value Error
A cal value error occurs when a calibration value sent
over the bus (L command) exceeds the capabilities of the
amently selected range. For example, sending a cslibra-
tion value of 2mA on the 200@ range will cause a cal
vslue error. The following message is briefly displayed
when this error o-:
CAL VALUE
Cal Emor
A cal error indicates that calibration resulted in a cal con-
stant value which is not within allowable limits. In the
event of this error, the old cal constants are used. To clear
the following displayed error messages, press any front
panel key.
CAL ERROR
Cal Lock Error
When the CAL LOCK switch (accessed from the rear
panel) is in the locked (out) position, calibration is dis-
abled. Sending a calibration value (L command) over the
bus will cause the following message to be briefly dis-
played:
CAL Lcxx
The calibration command will be ignored.
Conflict Error
A conflict error pertains to the voltage source of the
Mode1487. This ezmr occurs when trying to
program the
voltage source (using the V command) to a level that ex-
ceeds the limits of its selected range. When this error oc-
curs, the following message is briefly displayed:
CONFLICT
4-50
The voltage source command is ignored.
4.7.2
IEEE-488 Status Indicators
The REM (remote), TALK (talk), LSTN (listen), and SRQ
(service request) indicators show the present IEEE-488
status of the instrument. Each of these indicators is
briefly described below.
- I - -
REM TALK LSTN SRQ
REM-As the name implies, this indicator shows when
theinstrumentisintheremotestate.NotethatREMdoes
not necessarily indicate the state of the REN line, as the
instrunentmustbeaddressed tolistenwithRENtruebe-
fore the RRM indicator turns on. When the instrument is
in remote, all front panel keys except for the LOCAL key
arelockedout. Whenmistuned off, theinstrunentis
in the local state, and front panel operation is restored.
TALK - This indicator is on
when the instrument is in
the talker active state. The unit is
placed in this state by
addressing it to talk with the correct h4TA (My Talk Ad-
dress) command. TALK is off when the unit is in the
talker idle state. The instrument is placed in the talker
idle state by sending it an UNT (lJnts&) command, ad-
dressing it to listen, or with the IFC (Interface Clear)
com-
mand.
LSTN -This indicator is on
when
the Model 4%/4S7 is
in the listener active state, which is activated by address-
ing the instrument to listen with the correct MLA (My
Listen Address) command. Listen is off when the unit is
in the listener idle state. The unit can be placed in the lis-
tener idle state by smding UNL (Unliaten), addressing it
to talk, or by sending IFC titerface Clear) over the bus.
SRQ- The instrument can be programmed to generate a
service request (SRQ) when one or more errors or condi-
tions occur. when this indicator is on, a service request
has been generated. This indicator will stay on until the
serial poll byte is read. See paragraph 42.11 for details.