Keithley 2790, Reference Manual

Page: 231 / 568

7-26 Model 2790 SourceMeter
®
Switch System Reference Manual
Remote programming — scanning
klqb
Scanning examples (remote programming and front panel operation) are pro-
vided at the end of this section.
7702 module scanning
Trigger model
The trigger model for bus operation is shown in Figure 7-2 . Bus operation is similar to
front panel SCAN operation, with the following significant differences:
Idle — The instrument goes into the idle state (measurements halted) after the last scan chan-
nel is measured. For front panel operation, the instrument stays in idle until the next scan is
started. For bus operation, the instrument will not stay in idle unless continuous initiation is
disabled. There are two commands to disable continuous initiation:
INITitate:CONTinuous OFF ' Disable continuous initiation.
*RST ' Restore *RST defaults.
The instrument will remain in idle until it receives an initiate command. Typical com-
mands to initiate one scan cycle include:
INITiate ' Initiate one scan cycle.
READ? ' Initiate one scan cycle and request "sample" readings.
More information on using these commands is provided by Reference f that follows
Table 7-1 .
Control sources — For bus operation, there are two additional control sources: Bus and
Manual. For the Bus control source, scan operation is controlled by bus triggers (i.e.,
*TRG) or by using the TRIG key. For the Manual control source, event detection is con-
trolled solely by the TRIG key. Note that the instrument has to be in local in order to use
the TRIG key. The LOCAL key takes the instrument out of remote.
Trigger and sample counters — For front panel SCAN operation, the number of chan-
nels in the scan list and the programmed reading count automatically sets the trigger and
sample counters. For remote operation, these two counters are set by the
TRIGGer:COUNt and SAMPle:COUNt commands.
klqb
To set sample count >1, continuous initiation must be disabled (see “Idle”
page 7-7 ). Note that only sample count readings are stored in the buffer. See
Section 8 for detailed information on the trigger model.