Keithley 708A Instruction Manual Download

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IEEE-488 Programming

5-8

To simulate the error condition, disconnect a DIN cable from
either of the MASTER/SLAVE connectors. The condition is
detected when the Model 708A performs the next operation
that requires communication among the units. A master/
slave error is flagged in the U1 word, as discussed in para-
graph 5.9.20.

Not in remote error

A not in remote error occurs if the instrument receives an
“X” while it is in the local state. This is caused by failing to
set the REN line true before addressing the Model 708A to
listen. A not in remote error is flagged in the U1 word, as dis-
cussed in paragraph 5.9.20.

Trigger before settling time error

A trigger before settling time error occurs when the instru-
ment receives an additional trigger before the settling time
has expired. This time period is after assertion of the
READY signal and before assertion of the MATRIX
READY signal. See paragraph 4.8 for a complete discussion
of trigger timing. Both READY and MATRIX READY are
bits in the SPOLL byte; MATRIX READY is also a rear pan-
el signal. Note that a master/slave error is also flagged in the
U1 word, as discussed in paragraph 5.9.20.

A trigger during this time period is processed normally.

RAM or ROM failure

A RAM or ROM failure occurs when the power-up routine
detects an error, either a RAM error or a checksum error in
program ROM. If an error is detected, the error LED (ERR)
is lit (cleared by any keypress).

Setup error

A setup error occurs when the Model 708A power-up routine
detects a checksum error in one or more setups stored in non-
volatile memory. If an error is detected, the error LED (ERR)
is lit and the affected setups are cleared to all open. A key-
press will clear this error. Note that a setup error is also
flagged in the U1 word, as discussed in paragraph 5.9.20.

Trigger overrun (hardware) error

A trigger overrun occurs when the instrument is triggered
while it is still processing a setup change from a previous
trigger and before the READY (for trigger) signal is asserted.
READY is a bit in the SPOLL byte. See paragraph 4.8 for a
complete discussion of trigger timing. The exact trigger
stimulus depends on the selected trigger source, as discussed
in paragraphs 4.8.5 and 5.9.19.

Overrun triggers do not affect the instrument except to gen-
erate the error. In other words, the present setup change is not

aborted by the overrun trigger stimulus, and the trigger is
ignored. Note that a trigger overrun error is also flagged in
the U1 word, as discussed in paragraph 5.9.20.

5.7.2 Status indicators

The TALK, LSTN, and REM indicators show the present
IEEE-488 status of the instrument. Each of these indicators
is described below.

TALK

— This indicator is on when the instrument is in the

talker active state. The unit is placed in this state by address-
ing it to talk with the correct MTA (My Talk Address) com-
mand. 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 (Untalk) command, addressing it to listen, or with
the IFC (Interface Clear) command.

LSTN

— This indicator is on when the Model 708A is in the

listener active state, which is activated by addressing the in-
strument 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 listener idle state by send-
ing UNL (Unlisten), addressing it to talk, or by sending IFC
(Interface Clear) over the bus.

REM

— This indicator shows when the instrument is in the

remote state. Note that REMOTE does not necessarily indi-
cate the state of the REN line, as the instrument must be ad-
dressed to listen with REN true before the REMOTE
indicator turns on. When the instrument is in remote, all front
panel keys except for the LOCAL key are locked out. When
REMOTE is turned off, the instrument is in the local state,
and front panel operation is restored.

SYSTEM

TALK

LSTN

REM

ERR

COPY

DISPLAY

OUT

COPY

Figure 5-7

IEEE-488 indicators

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