BOP HIPWR 111315 3-613.6.4 PROGRAM MESSAGE STRUCTURESCPI program messages (commands from controller to power supply) consist of one or moremessage units ending in a message terminator. The message terminator is not part of the syntax; itis defined by the way your programming language indicates the end of a line (“newline” charac-ter). Sending a character with EOL line asserted is another way of sending a message termina-tor. The message unit is a keyword consisting of a single command or query word followed by amessage terminator (e.g., CURR? or TRIG). The message unit mayinclude a data parameter after the keyword separated by a space; the parameter is usuallynumeric (e.g., CURR 5), but may also be a string (e.g., OUTP ON). Figure3-19 illustrates the message structure, showing how message units are combined. The follow-ing subparagraphs explain each component of the message structure.NOTE: An alternative to using the message structure for multiple messages defined in the fol-lowing paragraphs is to send each command as a separate line. In this case each com-mand must use the full syntax shown in Appendix B.FIGURE 3-19. MESSAGE STRUCTURECURR:LEV 3.5;:OUTP ON;:CURR?MESSAGE TERMINATORKEYWORDQUERY INDICATORROOT SPECIFIERMESSAGE UNIT SEPARATORDATAKEYWORDKEYWORDKEYWORD SEPARATORKEYWORDMESSAGE UNIT SEPARATORDATAMESSAGE UNITDATA SEPARATORDATA SEPARATORROOT SPECIFIER
