GE PACSystems RX7i, User Manual

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Chapter 5. Ethernet Global Data
72 PACSystems* RX7i & RX3i TCP/IP Ethernet Communications User Manual GFK-2224Q
Valid Memory Types for Ethernet Global Data
The PLC memory types listed below can be included in EGD exchanges.
Memory Type Description
P-Producer
C-Consumer
%R Register memory in word mode P/C
%W Word memory in word mode P/C
%AI Analog input memory in word mode P/C
%AQ Analog output memory in word mode P/C
%I Discrete input memory in byte mode P/C
%Q Discrete output memory in byte mode P/C
%T Discrete temporary memory in byte mode P/C
%M Discrete momentary memory in byte mode P/C
%SA Discrete system memory group A in byte mode P/C
%SB Discrete system memory group B in byte mode P/C
%SC Discrete system memory group C in byte mode P/C
%S Discrete system memory in byte mode P
%G Discrete global data table in byte mode P/C
Symbolic Variables Symbolic variables P/C
Discrete point references such as %I or %Q are configured as Byte-Array, Word-Array, or Dword-Array
variables. That means a variable with discrete point references must be defined in blocks of 8 points if it is
defined as a Byte-Array, 16 points if Word-Array, and 32 points if Dword-Array. Discrete memory must be byte-
aligned.
Boolean type and Boolean-Array variables are not allowed.
To use a symbolic variable in an EGD exchange, it must exist in the Variables definition for the target. To add it
to an exchange, double click the Variable field to open a selection dialog box.
Figure 35: Adding Symbolic Reference to Ethernet Global Data Exchange
Planning Exchanges
It is possible to configure more Ethernet Global Data than a PLC can transfer (especially on 10Mbit networks). If
high levels of consumer timeouts occur in some or all of the consumed exchanges, the EGD load can be
reduced by:
▪
Increasing the production period (especially if the period is more frequent than double the minimum time in
which the data is needed).
▪
Defining fewer exchanges, each with more data.