Programming Overviav - Keithley 595 Instruction Manual

4.9 DEVICE-DEPENDENT COMMANDS
This section contains the information needed to control the Model 595 over the IEEE-488 bus using
the device-dependent commands. A programming example using the HP85 computer is included for
each device-dependent command.
It is assumed that the user is already familiar with front panel operation.
4.9.1 Programming Overview
IEEE-488 device-dependent commands (summarized in Table 4-6) are used with the Model 595 to con-
trol various operations including ftinction, razige~ and trigger. Each co nunand is made up of a single
ASCII letter followed by a number representing an option of that command. The number may be in
either an integer, decimal or exponential format. For example, a command to-control the measuring
function is programmed by sending an ASCII "F" followed by a number representing the function op-
tion. The IEEE-488 bus treats these commands as data in that ATN is fake when the commands are
transmitted.
A number of commands may be grouped together in one string. A cornman d string is usually terminated
with an ASCII "X" character, which tells the instrument to execute the comma? d string. Commands
sent without the execute character will not be executed ate that time, but they will be retained within
an internal command buffer for execution at the time the X character is received. If any errors occur,
the instrument will display appropriate front panel error messages and generate an SRQ if programmed
to do so when "X" is received.
Bus commands affect the Model 595 much like the fronts panel controls. Note that commands are not
necessarily executed in the order received. Thus, to force a particular command sequence, you would
follow each command with the execute character (X), as in the sample s&g, ZlXFlX, which will first
enable ZERO CHECK and then select the CURRENT function. If a particular command occurs n times
in a command string, then the "nth" occmrence is the only one used, i.e., RSR4R3X goes to R3x only.
Device-dependent commands can be sent either one at a time, or in groups of several commands within
a single string. Some -pies oft valid command strings include:
FOX-Single command string.
FORmOX-Multiple command string.
T6 X-Spaces are ignored.
Typical invalid command strings indude:
BIX-Invalid command, as B is not one of the instrument commands. (IDDC)
FZX-Invalid command option because 2 is not an option of the F co nunand. (IDDCO)
If an illegal device-dependent command (IDDC) or an illegal device-dependent command option
(IDDCO) is received, or if a comma d
"bF,rr" (bus error) will be displayed.
string is sent with REN false, the string will be ignored and
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