Reading Mode(B) - Keithley 193A Instruction Manual

3.10.9 Reading Mode (B)
The reading mode command parameters allow the selec-
tion of the source of data that is transmitted over the
IEEE488 bus. Throu h this command, the user has a choice
of data from the A /?I converter (normal DMM readings)
or the buffer (data store). The reading mode commands are
as follows:
80 = A/D Converter readings
81 = Data Store readings
Upon power-up or after the instrument receives a DCL or
SDC command, the Model 193A will return to the default
condition.
When in BO, normal A/D readings will be sent. In a con-
tinuous trigger mode, readings will be updated at the con-
version rate. The Bl command is used to access readings
from the buffer. When the 81 command is sent, subsequent
readings will be taken from consecutive buffer locations
beginnin
readings 8,
with the first memory location (001). Once all
ave been requested, the unit will cycle back and
begin again.
HP-85 Programming Example-From the front panel, store
some readings in the data store. Enter the following
statements into the computer to read the stored reading in
the first memory location of the buffer. The reading will
be displayed on the computer CRT.
The second statement above sets the instrument to the buf-
fer reading mode. The third and fourth statements acquire
the reading and display it on the CRT.
3.10.9 Data Store Interval (Q) and Size (I)
The data store is controlled by the interval command (Q)
and the size command (I). The storage process will start
when the appropriate trigger is received.
With the Q command, the user can select the interval that
the instrument will store readings or select the one-shot
mode. In the one-shot mode, one reading will be stored
each time the instrument is triggered. The Q command is
in the following form:
QO=One-shot into buffer
Qn=Set storage interval in millisec (lmsec to 999999msec)
To use the data store in the one-shot mode (QO), the in-
strument must be in a one-shot trigger mode (Tl, T3, T5
or T7). In the QCITI mode, one reading will be stored each
time the instrument is addressed to talk. In the QlJI3 mode,
each GET command will cause one reading to be stored.
In the QOT5 mode, each instrument execute character (X)
will cause a reading to be stored. Finally, in the QOT7 mode,
each external trigger pulse will cause a reading to be stored.
If the instrument is in a continuous trigger mode (PZ, T2,
T4 or T6), an IDDC error will occur.
To store readings at a selected interval (Qn), the instrument
can be in any trigger mode. When the selected trigger oc-
curs, the storage process will commence.
The size of the data store can be controlled by one of the
following I commands.
IO=Continuous storage mode.
In=Set data store size to n (1 to 500).
In the continuous data tom
stop after the buffer is fille 2
e mode (IO), storage will not
(500 readings), but will pro-
teed back to the first memory location and start overwriting
data. With the Innn command, the storage process will stop
when the defined number of readings have been stored.
In this case the buffer is considered to be full.
Notes:
1. With the instrument in the T6 or T7 external triaer mode,
the storage process can be started by pressing the front
panel TRIGGER button after the instrument is returned
to local operation (LQCAL button).
2. The data store is disable by sending an F command that
places the instrument in a different function.
3. The instrument must be in a valid operating state in order
to use the high speed data store capabilities. The high
speed intervals are lms, 2ms, 3ms and 4ms. Valid com-
mands are listed in Table 3-13.
4. With S2 or S3 asserted, the fastest valid storage interval
(I) is 40msec. An interval less than 40msec will result in
a short period error when the storage process is started.
Readings will be stored as fast as the instrument can run.
5. Either during or after the storage process, readings may
be recalled by using the Bl command as described in the
last paragraph. Also, the highest, lowest and average
reading in a full buffer can be recalled by sending the
appropriate U commands. See paragraph 3.10.18 for in-
formation on using the U commands.
3-22