6. REMOTE:
This command is used to set the 4278A to remote. When this command is sent
except for the LCL key the front panel will be disabled. If LOCAL LOCKOUT is
active then the front panel LCL key will also be disabled.
REMOTE 7: sets all devices on the port 7 to remote
REMOTE 717: sets the instrument addressed at 17 to remote.
7. SERIAL POLL:
This command places the status byte on the bus. The eight bits of the status
byte shows the 4278A's operating state. See paragraph 4-2-8 for more informa-
tion on the status byte.
Var=SPOLL(717): the instrument addressed at 17 is serially polled.
8. SERVICE REQUEST:
The 4278A is capable of generating a SRQ (Service Request) control signal when
it requires the controller to take action. A SRQ can be thought of as an interrupt
which informs the controller that information is ready to be transmitted, and an
error condition exists in the instrument. When the 4278A issues an SRQ it also
sets Bit 6 of the status byte. Bit 6 is the ROS (Request Service) bit, sometimes
referred to as the "status bit" in connection with polling. When the 4278A is
serially polled, it will clear the ROS bit and the SRO line, which is one of the five
management control lines of the system interface. Any bit in the status byte can
initiate an SRQ. The status byte may be masked by the user to determine which
bits caused the 4278A to set the SRO line. See paragraph 4-2-8 for more infor-
mation on the status byte.
4-7
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