Interface messages are transmitted to the instrument on the data lines, with the attention line being active (LOW). They serve to communicate between controller and instrument.
Universal Commands
Universal commands are encoded in the range 10 through 1F hex. They are effective for all instruments connected to the bus without pervious addressing.
Universal Commands
| Command | QuickBASIC command | Effect on the instrument |
| DCL(Device Clear) | IBCMD (controller%, CHR$(20)) | Aborts processing of the commands just received and sets the command processing software to a defined initial state. Does not change the instrument setting. |
| IFC(Interface Clear) | IBSIC (controller%) | Resets the interfaces to the default setting. |
| LLO(Local Lockout) | IBCMD (controller%, CHR$(17)) | Locks switchover from remote control to Local (manual control) by means of the front panel keys |
Addressed Commands
Addressed commands are encoded in the range 00 through 0F hex. They are only effective for instruments addressed as listeners.
Addressed Commands
| Command | QuickBASIC command | Effect on the instrument |
| GTL(Go to Local) | IBLOC (device%) | Transition to the "Local" state (manual control). |
Note:
The CMU can not be configured as a high-speed HS488 listener; the commands
CFE (Configure Enable) and CFGn (Configure) are not supported.