Chroma 61501, User Manual

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Remote Operation
8-5
Program Message Terminator (<PMT>):
A program message terminator represents the end of a program message. Three permitted
terminators are:
(1) <END> : end or identify (EOI)
(2) <NL> : new line which is a single ASCII-encoded byte 0A (10 decimals).
(3) <NL> <END> : new line with EOI.
Note: The response message is terminated by <NL> <END> for GPIB, and <NL> for
RS-232C.
Figure 8-1 The Structure of Command Message
8.4 Traversal of the Command Tree
Multiple program message unit elements can be sent in a program message. The first
command is always referred to the root node. Subsequent commands are referred to the
same tree level as the previous command in a program message. A colon preceding a
program message unit changes the header path to the root level.
Example:
OUTPut : PROTection : CLEar All colons are header separators.
: OUTPut : PROTection : CLEar Only the first colon is a specific root.
OUTPut : PROTection : CLEar; : VOLT : AC 100 Only the third colon is a specific root.
8.5 Execution Order
The AC source executes program messages by the order received. Program message
units except coupled commands are executed in order of reception. The execution of
coupled commands is deferred until program message terminator is received. A coupled
command sets parameters which are affected by the setting of other commands. Problems
may arise, because the prior state of the AC source will affect the response of a coupled
parameter to its programming.
For example, assume that the current output voltage range is LOW, a new state is desired
with output voltage range HIGH, and amplify 220 Volt. If the commands
VOLTage
: AC 220<PMT>
VOLTage : RANGe HIGH<PMT>