National Instruments GPIB-MAC User Manual page 45

November 1985
If this is the first function you call that requires GPIB
controller capability, and you have not disabled System
Controller capability with csc, the GPIB-MAC sends
Interface Clear (IX) to make itself CIC. It also asserts
Remote Enable.
Refer to Appendix D for more information on clearing
devices.
Refer to Appendix B for more error information.
Examples:
1. PRINT #l,"clr 14+30,16+12,18,3+26,6"
2. PRINT #l,"CLR"
34 SECTION FOUR - FUNCTIONS
'Selectively clear
'5 devices.
'Issue Device Clear
'to all devices.