SPI Programming Manual (G06.24+, H06.03+, J06.03+)

General SPI Programming Guidelines
SPI Programming Manual—427506-006
5-42
Defining the Context Token
Because the terminal name is a required part of the context, it is included in the context
token even though it is already present in the TERMNAME token. This way, the
requester does not need special-case knowledge about which tokens must be provided
to continue the command. The requester always extracts the context token and
supplies it with the original command parameters.
If the server detects something wrong with the context or a mismatch between the
context and the new command, it should return a response record containing an error
number that identifies the problem, at least to the extent that the problem concerns the
Figure 5-1. Response Continuation for a Typical Information Command
VST021.vsd
<INFO> <TERM> <+>
<INFO> <TERM> <$a> <token> <token> <$a>
Terminal
Name
Requester Subsystem
Context
<INFO> <TERM> <$b> <token> <token> <$b>
Terminal
Name
Requester Subsystem
Context
<INFO> <TERM> <+> <$a>
Context
<INFO> <TERM> <$last> <token> <token>
Terminal
Name
Requester Subsystem
<INFO> <TERM> <+> <$x>
Context
!
!
!