Keithley 194 Instruction Manual page 114

IEEE-488 PROGRAMMING
As an example, let us compare the T2 (continuous, GET)
and T3 (single, GET) modes. Sending TW will arm the AID
converter, at which point the unit will be processing data,
waiting for the GET trigger stimulus. When GET is re-
ceived, the unit will process a single measurement, warm
the A/D converter, and then wait for another GET com-
mand before taking another measurement. Note that it is
not necessary to send T2X again before triggering another
measurement. In contrast, you must send a 'I3X command
before every GET when using that trigger mode. The same
general rule applies when comparing the remainder of the
trigger modes listed in Table 4-13.
A number of the trigger modes, including external, input
signal, and other channels are also available from the front
panel. When using these modes over the bus, it is not
necessary to press TRIGGER to arm the A/D converter as
arming takes place when the command in question is
received.
A/D Trigger Modes
The trigger modes for the A/D modules are paired accor-
ding lo the type of trigger stimulus as follows:
Talk (Tl) and Tl~): 'The measurement will be triggered when
the unit is addressed to talk over the bus.
GET (T2 and T3): The IEEE-488 multiline GET command
provides the trigger in these two modes.
X (T4 and TS): The X (execute) character triggers the
instrument.
External (I'6 and T7): An appropriate pulse, applied to the
external trigger input jack, triggers the unit (see paragraph
3.6.7).
Positive Slope (T20,m and T21,m) The unit will be triggered
when the input signal rises to a level programmed by the
m parameter. Note that m is given in volts.
Negative Slope (T22 and T23): The instrument will be trig-
gered when the input signal drops to a level programmed
by the m parameter. Again, m is given in volts.
Other Channel (T24 and T25): Triggering takes place when
the other channel is triggered. The method used to trig-
ger the other channel depends on its programmed trigger
mode. This mode is available only if the Model 1944
module is installed in the channel 2 location.
Immediate (T25 and T27): Sending these commands will
provide the necessary stimulus in these two modes.
Plotter control: T30 and 'I31 provide methods to initiate and
stop plotting via the analog output. The appropriate ac-
tion will take place when the command is received.
NOTES:
1. Omitting the trigger level parameter, m, in the TZO-T23
command strings will result in a trigger level of OV.
2. The talk, X, and GET trigger modes can be verified from
the front panel with the SOURCE key (press LOCAL
first to cancel REMOTE). The instrument will then
display one of the following messages, as appropriate:
3
TRIG ON X
'TRIG ON TALK
TRIG ON GET
Note that these trigger sources are available only over
the bus; if you continue to press uprangeidownrange,
you will change the trigger source.
I'rogramming the AID converter (for example, chang-
ing range) after it has been armed will disarm the con-
verter. To warm the converter under these conditions,
send the appropriate trigger command. For example, in-
stead of l3XROX, send ROXlJX. You can program non-
A/D parameters such as SRQ without disarming the
converter.
HP-85 Programming Example-Place the instrumrnt in the
single, G!ZT trigger mode with the following statements:
F:EI,OTE 'Fii'3
The instrument can now be triggered by sending GBI' with
the following statement:
1-F: I 1; I;ER '71'5
When the above statement is executed, the instrument will
perform a single measurement sequence.
Model 6573 Programming Example-Place the instrument
in the single, GET trigger mode by using the following
statements:
4-24