ICS N4865A, Инструкция по эксплуатации

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3-2
3
If AutoFind is disabled and the N4865A has been confi gured to use a specifi c
oscilloscope IP address, then the N4865A does not do a UDP broadcast and
instead attempts to communicate directly with a VXI-11.3 oscilloscope at the
designated IP address.
When the N4865A fi nds a VXI-11.3 compatible oscilloscope it opens a core
and abort channel to the oscilloscope. The N4865A will also set up a reverse
Interrupt channel if the oscilloscope supports it.
The N4865A's RDY LED blinks during the oscilloscope discovery process,
which can last an indefi nite period of time, and becomes solid on when the
N4865A links with a LAN oscilloscope and becomes ready to transmit GPIB
Commands and Device Messages. The RDY LED will stay on until the N4865A
fails to receive a reply to a device RPC. If the N4865A looses connection with
the oscilloscope, it will attempt to reconnect to the oscilloscope.
3.2.2 GPIB Operation
The N4865A only operates correctly with an IEEE-488.2 compatible GPIB
Controller. All device messages sent to the N4865A must be terminated with
EOI asserted on the last character as the N4865A does not check for message
terminators. The N4865A will assert EOI when it outputs the last character in
the response received from the LAN oscilloscope if the END bit was asserted
in the response packet.
When the N4865A receives a terminated device message from the GPIB bus
the N4865A sends the data to the companion oscilloscope with the device_write
RPC. The N4865A holds the GPIB bus while transmitting the data to the com-
panion oscilloscope. In the case of large messages, the N4865A sends the data
to the companion oscilloscope when its GPIB listen buffer becomes full. When
the fi rst buffer load of data has been sent to the companion oscilloscope, the
N4865A accepts the next buffer worth of data. The process repeats with the
N4865A handling a buffer worth of data at a time until the N4865A receives
the last portion of the data with EOI asserted on the last byte. Unterminated
device messages are normally not sent to the companion oscilloscope and are
discarded when the N4865A becomes an active talker or is sent a GPIB clear
or trigger command.
When the N4865A is made an active talker, it sends a device_read RPC to the device_read device_read
companion oscilloscope to read the expected data. When the N4865A receives
response data from the companion oscilloscope that is terminated with END
asserted in the response packet, the data is output on the GPIB bus with EOI