Keithley 194 Instruction Manual page 119

IEEE-488 PROGRAMMING
Obtaining Data
Before the instrument will transmit its data string, it must
be properly addressed to talk by the controller. The basic
controller sequence for requesting data is as follows:
1. The controller sets the ATN line true.
2. The Model 194 is addressed to talk by placing the ap-
propriate talk command byte on the data lines. For the
default primary address (9), the correct talk command
byte is $49.
3. The controller places the ATN line false.
4. The controller then begins its input sequence and in-
puts data bytes in succession until all are taken. General-
ly, the sequence will cease when the terminator is
detected. Some controllers terminate on EOI.
Generally, data is placed into a string or numeric variable
as the bytes are received. For example, a typical sequence
for the HP-85 computer is:
In this instance, the complete reading string is placed in
the A$ variable. In cases where numeric input is required,
the instrument should be operated in a mode without a
prefix and suffix (Gl or G4, for example). Under these con-
ditions, readings can be placed directly into a numeric
variable as in the example below
A is the variable into which the numeric value is placed.
If the prefix and suffix are not eliminated with the correct
G command, an incorrect value may be placed into the
numeric variable.
In the G6 and G7 (binary modes), data bytes can be placed
into a string variable in a similar manner. However, some
form of algorithm must be used to convert data into
displayable form. Consult your controller's instruction
manual for details.
HP-65 Programming Example-Use the following program
to obtain and display an instrument data string.
COMMENTS
Place instrument in
rel"ote.
Select data format,
aveiagc mode.
Get reading fn,m
instrument.
Display the reading.
In this program, the instrument is first placed in remote
(line Id), and several operating mod& arc then prw
grammed. 'The instrument is placed in the GO data ior-
mat, average, and correct reading modes (line 20). x~ri d.&l
is then requested (line 30) and displayed (line 40). Sot?
that data with prefix, without suffix is displayed because
the instrument is in the GO mode.
Model 8573 Programming Example-Add the following
lines to the modified declaration file paragraph (4.6.3) and
run the resulting program to obtain and display an instru-
ment data string.
In the above program, the instrument is placed in rem<jtc
(line 10) and then programmed for data format, wav~fwn~,
and reading modes (line 20). A rwding is then rcquestcd
(line 40) and then displayed (line SO).
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