Rockwell-automation 5370-UPK CVIM USER-PAK Option Manual de usuario descargar pdf (Pagina 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

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Rockwell-automation 5370-UPK CVIM USER-PAK Option Manual de usuario Pagina 49