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Model 8902A
Operation
Clearing the Status Byte
NOTE
Remolt>-to-Local transitions will not clear the Status
Byte.
Once bits in the Status Byte are set, they can be cleared
by
the following operations.
0
Reading the Status Byte
by
serial polling AFTER the condition is cleared. If the condition
which set the bits persists, those. bits and the RQS bit will again be set.
0
Sending the Device Clear (DCL) message, presetting
or
powering up the instrument.
0
In Talk Status Only, the Status Byte is cleared each time the one-byte Data message is issued
to the bus
0
Sending the Serial Poll Disable
(SPD)
bus command, or
Sending the Abort message.
Abort
Abort abruptly terminates all listener/talker activity on the interface bus and prepares all instruments
to receive a new command from the controller. Typically this is an initialization command used to
place the bus in a known starting condition. The Measuring Receiver stops listening o r talking when
it receives the Abort message.
Pass Control/Take Control
The Measuring Receiver does not respond to the Pass Control/Take Control message because it
cannot act as a controller.
Status Bit
The Measuring Receiver does not implement parallel poll operations and therefore cannot send the
Status Bit message. The Status Bit should not be confused with the Status Byte which was discussed
previous1 y under "Status Byte".
3-1 1. ADDITIONAL INFORMATION
Annunciators
REMOTE Light: Lights when the instrument is operating in remote mode. When the Measuring
Receiver goes to local operation, the front-panel REMOTE annunciator turns
o f f .
LISTEN Light: Lights when the instrument
is
addressed to Listen.
TALK Light: Lights when the instrument is addressed
to Talk.
SRQ
Light: Lights when the Service Request message has been sent (SRQ line true), and the front
panel has been updated.
3-33
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