Rockwell Automation 5370-UPK CVIM USER-PAK Option - Manual (Page 49)

Chapter 6
Creating Custom Serial Port Messages
6–7
Picking the Buffer box toggles the setting between Buffer: Wait and Buffer:
No wait.
Buffer: Wait
The two Buffer box settings are described below:
•
Buffer: Wait – With Buffer: Wait selected, the CVIM transmits your
custom serial port messages with priority over inspection triggers. That
is, if one or more inspection triggers are received while the CVIM is
waiting to transfer a serial port message to the buffer, the received triggers
are rejected while the CVIM completes the message transmission. This is
a concern mainly if the trigger rate is fast enough, and the serial message
transmissions are long enough, to cause triggers to be rejected.
Note: When a trigger is rejected, the Trigger Missed bit is set, and the
missed trigger count is incremented. (see the chapter on remote I/O in the
CVIM Communications Manual for more information on discrete bits).
An advantage to selecting Buffer: Wait is that the serial messages can be
as lengthy as the time between triggers permits, and as lengthy as CVIM
memory allows. A disadvantage is the possibility that, in some cases,
some triggers may not be processed.
Buffer: No wait
•
Buffer: No wait – This is the default setting. With Buffer: No wait
selected, the processing of inspection triggers has priority over the serial
port message transmissions.
The Buffer: No wait setting imposes a message size restriction. Due to
the size of the internal buffer, the combined length of all serial messages
to be transmitted for a single inspection must be no greater than 128
bytes; serial messages with a combined length greater than 128 bytes will
not be transmitted when
Buffer: No wait is selected.
With Buffer: No wait selected, when a trigger is received, the CVIM
processes all of the strings defined for a serial port; if the content of all
serial messages to be transmitted does not fit into the buffer (either the
message is greater than 128 bytes, or the buffer is not completely empty
yet) the message is immediately discarded.
Note: The serial messages are always transmitted in full, or not at all – a
message is never partially transmitted.
The advantage to selecting Buffer: No wait is that no triggers are ever
rejected due to transmission of your custom serial port messages
(however, regardless of the
Buffer: box setting, processing of serial port
strings does impact the CVIM inspection analysis time). Disadvantages
are that the total combined length of all serial messages to be transmitted