Remote Control Basics
R&S
®
SMB100A
242
Operating Manual 1407.0806.32 ─ 21
●
The total cable length is restricted to a maximum of 15 m; the cable length between
two instruments should not exceed 2m.
●
A wired "OR"-connection is used if several instruments are connected in parallel,
since the slowest instrument determines the speed.
Any connected IEC bus cable must be terminated by an instrument or controller.
6.1.6.1
GPIB Interface Messages
Interface messages are transmitted to the instrument on the data lines, with the atten-
tion line (ATN) being active (LOW). They are used for communication between the
controller and the instrument and can only be sent by a computer which has the func-
tion of a GPIB bus controller. GPIB interface messages can be further subdivided into:
●
Universal commands
: act on all instruments connected to the GPIB bus without
previous addressing
●
Addressed commands
: only act on instruments previously addressed as listeners
Universal Commands
Universal commands are encoded in the range 10 through 1F hex. They affect all
instruments connected to the bus and do not require addressing.
Command
Effect on the instrument
DCL (Device Clear)
Aborts the processing of the commands just received and sets the com-
mand processing software to a defined initial state. Does not change the
instrument settings.
IFC (Interface Clear) *)
Resets the interfaces to the default setting.
LLO (Local Lockout)
The LOC/IEC ADDR key is disabled.
SPE (Serial Poll Enable)
Ready for serial poll.
SPD (Serial Poll Disable)
End of serial poll.
PPU (Parallel Poll Unconfig-
ure)
End of the parallel-poll state.
*) IFC is not a real universal command, it is sent via a separate line; however, it also affects all instruments
connected to the bus and does not require addressing
Addressed Commands
Addressed commands are encoded in the range 00 through 0F hex. They only affect
instruments addressed as listeners.
Remote Control Interfaces and Protocols
