5
Functional description
Page 90
gas-lab
Q1
5.6.2
Data exchange
module
5.6.2.1
Function.
The
Data exchange
module controls the host side of the gateway functionality.
All data points that are available during operation and shall be forwarded to a
host must be positioned on registers or data blocks/data words for the host. It is
also possible to scale the value in a suitable way before forwarding it, depending
on the data type. Usually, the data to be forwarded is the content of DSfG data
elements that have been polled by the
DSfG
module via a DSfG query telegram.
The forwarding of the received DSfG data to the host is defined in the
Data
exchange
module. The data transport in the direction to the host is processed
cyclically. If a new telegram arrives from the DSfG side, the associated export
values will be updated. In addition to the specification of the destination in the
host, the description of the export value also defines the way of positioning the
data point in the host (e.g. size, scaling, limits, and bit position).
A particular import value describes for the reverse data flow direction at which
position in the host a data point shall be collected and in which way it shall be
converted. It can be defined in the parameterisation whether the transmission to
the DSfG side shall be cyclic or event-driven.
Any number of import values from the host can be combined to a job group. All
data points of a job group are always put into the transfer memory together and
simultaneously. However, only after all of them have been collected again once
more. Moreover, a job group may be linked with a trigger. A trigger is a defined
position in the host and initiates a new processing of a job when its content has
changed.