Measurement Computing Micro 488/EX rev.2.1 - Manual (Page 38)

Section 3 IEEE Operating Modes
3.4
ENTER Receive data from a bus device.
OUTPUT Send data to bus devices.
PASS CONTROL Give up control to another device which becomes the Active
Controller.
SPOLL Serial Poll a bus device, or check the Service Request state.
PPOLL Parallel Poll the bus.
PPOLL CONFIG Configure Parallel Poll responses.
PPOLL DISABLE Disable the Parallel Poll response of selected bus devices.
PPOLL UNCONFIGDisable the Parallel Poll response of all bus devices.
SEND Send low-level bus sequences.
RESUME Unassert Attention. Used to allow Peripheral-to- Peripheral
transfers.
3.4 System Controller, Not Active Controller Mode
After Passing Control to another device, the System Controller is no longer the
Active Controller. It acts as a Peripheral to the new Active Controller, and the allowed
bus commands and their actions are modified accordingly. However, it still maintains
control of the Interface Clear and Remote Enable lines. The available bus commands
and their actions are:
ABORT Pulse Interface Clear.
LOCAL Unassert Remote Enable.
REMOTE Assert Remote Enable.
ENTER Receive data from a bus device as directed by the Active
Controller.
OUTPUT Send data to bus devices as directed by the Active
Controller.
REQUEST Set own Serial Poll request (including Service Request)
status.
SPOLL Get own Serial Poll request status.