Response Electronics CL6011B Especificaciones descargar pdf (Pagina 70)

3Ć50 Theory of Operation: Communications

Original Ć June 1990CE4.2:CL6211

3.5 Communications

The Regulatory Controllers respond to communication request

messages by prioritizing certain requests as having more importance

than other requests. This allows the controller to respond to requests for

process critical information more quickly than other requests which are

not nearly as time critical.

The priority of different request messages can be viewed as fitting into

these two categories; Process Data requests and Maintenance Data

requests.

3.5.1 Process Data Communications

Certain request messages can be categorized as giving information

specifically related to the process under control. This data is called

Process Data. Some examples include:

H Process Variable

H Set Point

H Implied Valve Position

H Bias

H Ratio

H Mode

H Alarms

H Tracking (Implied Valve Position tracking, etc.)

H Limiting (SP limited, Implied Valve Position limited, etc.)

H Diagnostics (Detailed Device Status)

When the Regulatory Controllers receive a request for Process Data, this

message is processed at a higher priority internally than the Control

Task. The latest available information is immediately returned to the

requestor.

If a Process Data change request is received, such as a Mode change or

a SP change request, this request is processed immediately and a

response is immediately generated. The action required by this change

request is buffered internally to be acted on by the Control Task at then

next opportunity (e.g. the next FST scan cycle).

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Response Electronics CL6011B Especificaciones Pagina 70