Session And Subsession; One-Way Mode Communication Flow - Casio PX-320 Implementation Manual

18.1.2

Session and Subsession

Subsession
One Parameter Set can be transferred per subsession. Subsession transfers one Parameter Set or data that is broken down
into multiple packets for transfer, with EOD (End of Data) sent at the end to terminate the send.
Data is divided into multiple packets when a single Parameter Set is larger than a certain size. The Packet Number in the
packet's index field is used to indicate the sequential position of a packet relative to the other packets. Even if Parameter
Sets are small, they cannot be grouped together and sent as a single packet. A Parameter Set delimiter is always treated
as a packet delimiter for transfer.
Session
One Parameter Set or multiple Parameter Sets can be transferred by one session. A session can consist of one subsession
or multiple subsessions, with EOS (End of Session) sent at the end to terminate the send.
Regardless of whether there is a single Parameter Set or multiple Parameter sets, an actual bulk dump always takes the
form of a session, never a subsession only.
18.2

One-way Mode Communication Flow

A session starts with the receiving device sending a request using an OBR, or with the sending device sending OBS data.
The session ends after transfer of all the data in the parameter set being transferred by the sending device is complete.
Data is divided into multiple packets of 256 bytes or less each, and transfers them at fixed intervals (20 msec).
A final EOD informs the receiving device when the session is ended.
Data Receiver
(External Device)
OBR →
Other subsessions
Data Sender
(This Instrument)
←
OBS
(20 msec or greater interval)
←
OBS
(20 msec or greater interval)
←
OBS
(20 msec or greater interval)
:
:
←
EOD
:
:
←
EOS
Send Request (Optional)
Data Transfer
Data Transfer
Data Transfer
End of Data
End of Session
35
Operation