Response Messages - Keithley 2001 Operator's Manual

A. Each new program message must begin with the root command, unless it is optional (e.g., [:SENSe]).
B. The colon (:) at the beginning of a program message is optional and need not be used. Example:
C. When the path pointer detects a colon (:) it will move down to the next command level. An exception
D. When the path pointer detects a colon (:) that immediately follows a semicolon (;), it resets back to
E. The path pointer can only move down. It cannot be moved up a level. Executing a command at a
4. Using common commands and SCPI commands in same message: Both common commands and
SCPI commands can be used in the same message as long as they are separated by semicolons (;). A com-
mon command can be executed at any command level and will not affect the path pointer. Example:
5. Program Message Terminator (PMT): Each program message must be terminated with an LF (line
feed), EOI (end or identify) or an LF + EOI. The bus will hang if your computer does not provide this
termination. The following example shows how a multiple command program message must be termi-
nated:
6. Command execution rules:
A. Commands are executed in the order that they are presented in the program message.
B. An invalid command will generate an error and, of course, not be executed.
C. Valid commands that precede an invalid command in a multiple command program message will be
D. Valid commands that follow an invalid command in a multiple command program message will be
4.9.3

Response messages

1. Sending a response message: After sending a query command, the response message is placed in the
Output Queue. When the Model 2001 is then addressed to talk, the response message is sent from the
Output Queue to the computer. The following example in HP BASIC 4.0 demonstrates this process:
2001-900-01 Rev. K / August 2010
If the root is optional, simply treat a command word on the next level as the root.
:stat:pres
is when the path pointer detects a semicolon (;), which is used to separate commands within the pro-
gram message (see next rule).
the root level.
higher level requires that you start over at the root command.
:stat:oper:enab
:rout:open
executed.
ignored. Example:
:rout:open
:open all will execute. Harve is an invalid command and will generate an error. The scan
query will be ignored.
A response message is the message sent by the instrument to the computer in response to a query
command program message.
10 OUTPUT 716; ":rout:scan?"! Send query command.
20 ENTER 716; A$
30 PRINT A$
40
There are two special query commands that are used to read the Error Queue. As error and status
messages occur they are stored in the Error Queue. This queue is a first-in first-out (FIFO) reg-
ister. Either of the following two SCPI commands can be used to read the Error Queue:
= stat:pres
<NRf>; ptr <NRf>; *ESE
all; scan (@1:5) <PMT>
all; harve; scan?
! Address Model 2001 to talk.
! Display response message on CRT.
END
IEEE-488 Reference
<NRf>; ntr <NRf>
4-35