Hi There Im working with SCPI but am having some problem clarifying a few points from the IEEE 488.2 and SCPI 99 documents, I hope someone here may have the knowledge to help. My questions mainly involve the seperators of message unit and command headers 1) some documents I have looked at have specified starting all message units with a colon, others seems to show examples where this is not necessary... is there a reason for this? which is correct? for example: (note the colon between COMMand; and SUBSystem2) :SUBSystem:COMMand;:SUBSystem2:COMMand2; or :SUBSystem:COMMand;SUBSystem2:COMMand2; 2) Some examples in the SCPI 99 document seem to suggest that not using the preceding colon allows subsequent commands of the same command path, or level on the tree, to not require the reiteration of that path for each command, is that correct? for example: :SUBSystem1:COMMand1_1;COMMand1_2; is equal to :SUBSystem1:COMMand1_1;:SUBSystem1:COMMand1_2; ?? 3) should a common command (those starting with a *) be preceeded by a colon? Many Thanks

@wolf99 wrote: Hi There Im working with SCPI but am having some problem clarifying a few points from the IEEE 488.2 and SCPI 99 documents, I hope someone here may have the knowledge to help. My questions mainly involve the seperators of message unit and command headers 1) some documents I have looked at have specified starting all message units with a colon, others seems to show examples where this is not necessary... is there a reason for this? which is correct? for example: (note the colon between COMMand; and SUBSystem2) :SUBSystem:COMMand; : SUBSystem2:COMMand2; or :SUBSystem:COMMand;SUBSystem2:COMMand2; 2) Some examples in the SCPI 99 document seem to suggest that not using the preceding colon allows subsequent commands of the same command path, or level on the tree, to not require the reiteration of that path for each command, is that correct? for example: :SUBSystem1:COMMand1_1;COMMand1_2; is equal to :SUBSystem1:COMMand1_1;:SUBSystem1:COMMand1_2; ?? 3) should a common command (those starting with a *) be preceeded by a colon? Many Thanks It has been awhile since I did SCPI, but here's what I'm quickly gathering from some of my old code. And some instruments are slightly different, so double check with the instrument before diving in head first. 1 & 2. The colon is the start of a command level. Not having the colon lets the instrument know that the command is at the same hierarhcial level. So, yes, you are correct with #2. However, some instruments will take commands without the colon. Power supplies, for example, will sometimes take VOLT 5.0 to set to 5V even though the voltage setting is several layers deep in the command set. 3. No colon needed for the special commands such as *RST and *IDN?.

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Ah yes. I have seen where i have gone wrong.

Thank you

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