GE VersaPoint IC220PB001, User Manual

Page: 123 / 202

GFK-1911B Chapter 8 Communications 8-3
8
PCP Communication Basics
The NIU can use PCP (Peripherals Communication Protocol) to exchange
parameter data in a local bus, with certain intelligent modules, such as the RS-
485/422 Communications Module (IC220BEM485) and the RS-232
communications module (IC220BEM232).
Device Parameter Data
Device parameters are data that is provided to intelligent PCP devices during the
startup phase of machines and systems. Once the parameters are entered, the
data only has to be modified upon a change in the parameterization or in the event
of an error. The parameters are described in the individual module documentation.
Device-specific parameters for all PCP devices can be modified via the parameter
data channel.
The Object Dictionary
Each PCP device that exchanges information via the parameter data channel has
its own
Object Dictionary . The Object Dictionary includes:
▪
Each parameter’s identifying Index number. The index is the address of the
communication object. It is required to identify the object.
▪
An Object Description of the parameter features. The Object Description
includes all the properties of the object, such as data type, object type, name,
etc. An example Object Description is:
Index Number Type Object Type Name
... ... ... ...
60 4A
hex
Ramp Record Speed quick stop
60 4B
hex
Integer16 Array Setpoint factor
... ... ... ...
Object Types include:
Simple variable-type objects such as measured values, time, or device status.
Arrays , consisting of multiple simple variable objects of the same type that are
grouped to form one object. Each element can be accessed individually. An
example of an array is a range of the same type of measured values.
Records , consisting of multiple simple variable objects of different type that
are grouped to form one object. Each element of a record can be accessed
individually. An example of a record is the group of data in a test report that
contains actual measured values and also the time of the measurements.
Program-invocation type objects that cause program sequences to run.