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Free-Run/Triggered
The counter can work in two different ways:
1.
Free-Run, where it starts a new measurement as
soon as the previous measurement is finished.
The first measuring result that is ready after the counter re-
ceives a read command, will be sent to the controller.
When the result has been read, the output buffer is reset
to zero until a new result is ready. One and the same
measuring result can only be read once.
2.
Triggered, where the counter waits for trigger com-
mand GET or 'X' from the controller before it
starts a measurement. When the measurement is
completed, the counter will wait until the controller
reads the measuring results, then the output buff-
er is reset. The function is the same as when
Displ Hold is selected from the front panel and
you start a new measurement by pressing the re-
set button.
Free-Run
Command Comment
Off
FRUN OFF
On
FRUN ON
Free-Run ON or OFF will not be indicated on the display.
When the counter switches to LOCAL, Free-Run will al-
ways be ON but when the counter switches back to re-
mote, it will return to its previously programmed settings.
Time-Out
When Free-Run is switched off it is possible to set a time-
limit (time-out) between the start of a measurement and
the time when a result is expected to be ready. If no result
is achieved before the set time is out, the counter can out-
put a Service Request, SRQ. Time-Out must be selected
in the SRQ-mask; see 'Service Request'. The program-
ming command is TOUT <number>. The timeout can be
set to any value between 100 ms and 25.5 s, the minimum
increment is 100 ms.
Time-Out
Command Comment
100 ms
TOUT 0.1
Off
TOUT 0
Time-Out is not indicated on the display. When the
counter switches to LOCAL, Time-Out is off, but when
switched to remote again, the set Time-Out will be active
again.
Time-out can be switched on when free-run is on but it
*
will not serve any purpose.
PM 6666 - OPERATORS MANUAL
GPIB-INTERFACE OPERATION
This function is sometimes
called Triggered-Mode
TRIG OFF gives the same
result. Default.
Time-Out is only intended
to be used with Free-Run
off
.
*
Always send this command
when Free-Run is switched
on. Default.
Bus Triggering
'X' will always cause the counter to start a new measure-
ment. X will work as group execute trigger, GET. 'X' must
always be placed in the end of a program message.
Service Request
The counter can send a service request, SRQ, when it
wants service from the controller. After an SRQ, the con-
troller must execute a serial poll which means that it must
ask each of the instruments for status information until it
finds the SRQ-giving instrument, evaluate the Status-byte
of the instrument and then make a decision what to do.
To enable the counter to send service requests, you must
set an SRQ-mask telling the instrument which conditions
will cause SRQ.
Command
Comment
MSR <number>
<number> is a decimal value
depending on selected SRQ reasons.
Decimal
Bit
value
7
128
6
64
5
32
4
16
3
8
2
4
1
2
0
1
*If SRQ for Measuring result ready is selected, the counter
will stop and wait until the controller fetches the result be-
fore a new measurement can start.
Write down the binary word for the required SRQ, then
convert it to a decimal value and insert the value as
<number>.
EXAMPLE:If you want SRQ to be sent when the time-out
elapses, when the counter is ready for triggering and
when the result is ready, the binary word required is
01000011 which is decimal 67; see table below.
Value if the
Bit
bit is 1
Example
Binary
word
7
128
6
64
5
32
4
16
3
8
2
4
1
2
0
1
Send MSR 67 to the counter.
Reason for SRQ.
Not used.
Time-Out.
Hardware fault.
Programming error.
Measuring stop enable.
Measuring start enable.
Ready for triggering.
Measuring result ready
*
Decimal
value
0
0
1
64 Time-Out
0
0
0
0
0
0
0
0
1
2 Ready to trigger
1 Meas. result
1
+
ready
67
.
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