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Back to : 4072-1,0.pdf | HomeEliminating Common SCPI Errors Roger Chaplin May 17, 1993There are three SCPI errors which occur more often than any others: -113, "Undefined header" -410, "Query INTERRUPTED" -420, "Query UNTERMINATED"This paper gives likely causes for these errors, and ideas for avoidingthem.-113, "Undefined header"------------------------This error indicates that what you sent to the instrument did notcontain a recognizable command name. The most likely causes for thisare:1. Missing space between the command and its parameter. Theremust be one or more spaces (blanks) between the command and itsparameter. For example: :sens:volt:dc:rang100 wrong :sens:volt:dc:rang 100 right2. Improper short or long form. Check the manual or the QuickReference Guide for the correct command name.3. Blanks (spaces) within the command name. Blanks are notpermitted within the command name. For example: :syst:err? right :syst: err? wrong-410, "Query INTERRUPTED"-------------------------This error occurs when you have sent a valid query to the instrument,then send it another command or query, or a Group Execute Trigger (GET)before it has had a chance to send the entire response message(including the line-feed/EOI terminator). The most likely causes are:1. Sending a query to the instrument and then sending anothercommand or query before reading the response to the first query. Forexample, the following sequence of commands will cause an error -410: send syst:err? send *opc?because you must read the response to syst:err? before sending anothercommand or query.2. Incorrectly configured IEEE 488 driver. The driver must beconfigured so that when talking on the bus it sends line-feed with EOIas the terminator, and when listening on the bus it expects line-feedwith EOI as the terminator. See the reference manual for yourparticular IEEE 488 interface.-420, "Query UNTERMINATED"--------------------------This error occurs when you addess the instrument to talk and it hasnothing to say. The most likely causes are:1. Not sending a query. You must send a valid query to theinstrument before addressing it to talk. This is true even ofmeasuring instruments, such as the Model 2001. You cannot get areading from the 2001 until you send it a query.2. Sending an invalid query. If you have sent a query and stillget this error, make sure that the instrument is processing the querywithout error. For example, sending an ill-formed query whichgenerates an error -113, "Undefined header" and then addressing theinstrument to talk will generate an error -420, "Query UNTERMINATED" aswell.3. Valid query following an invalid command. This can occur whenyou send mutiple commands or queries (program message units) within onecommand string (program message). When the Model 2001 detects an errorin a program message unit, it discards all further program messageunits until the end of the string. For example, in the followingprogram message: :sens:date?;:sens:func?the first program message unit :sens:date? will generate error -113,"Undefined header", and the Model 2001 will discard the second programmessage unit :sens:func? even though it is a valid query. NOTE: Thereare plans to modify the behavior of our SCPI instruments, such thatqueries following an erroneous program message unit do not getdiscarded, but commands do. This feature will be listed in the releasenotes for existing products when new firmware contains thismodification, and in the User Manual for new products.