With the one-way mode, the sending device sends data and ends the session without regard to the
response of the receiving device. This mode is best for one-way transfers from a sequencer or similar
device.
With the handshake mode, the sending device sends the data and then waits for a response from the
receiving device before advancing to the next session. This is a high-speed mode in which there is no
time wasted waiting.
See “VI Parameter Set List” for details about Instrument parameter sets.
18.1.2
Session and Subsession
Subsession
“One subsession” refers to transfer of one parameter set.
A subsession transfers one
parameter set or a parameter set that has been divided into multiple packets for transfer, with ESS (End
of Sub-session) at the end to terminate the send. Division of a parameter set into multiple packets is
used when the size of the parameter set is greater than a prescribed size. The packet number in the
packet index field indicates the sequential position of a packet relative to the other packets. A single
packet cannot be used to transfer multiple small parameter sets. A parameter set delimiter always must
be transferred as a packet delimiter.
Session
“One session” refers to a series of processes that occur for one user operation. One subsession
or multiple subsessions make up a session. The sender sends EBS (End of Bulk Dump Session) to
end a session. Regardless of whether there is a single parameter set or multiple parameter sets being
transferred, a bulk dump always takes the form of a session, never a subsession only.
18.2
One-way Mode Communication Flow
A single session starts when an external device, which wants to start communication for data send/receive
using one-way protocol, sends an SBS (Start of Bulk Dump Session) message to this Instrument, which
is its communication partner. The external device starts a request send using OBR or a data send using
OBS. The sub session ends when one parameter set that needs to be transferred by the data send device
is complete. After the send of all the parameter sets is complete, the external device that started the
communication sends an EBS to inform the Instrument that the session is ended. The transfer messages
of a single parameter set cannot exceed a preset size. To do this, messages are split into multiple packets
that are less than the preset size, and transfer is performed according to a preset interval. The preset
size and preset time are determined in accordance with the parameters described under “20.2 System
Exclusive Protocol Parameter”.
18.2.1
Example: Sending Data from the Instrument to an External Device in Response
to a Request from the External Device
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