GE GFK-0787B Manuel D’Utilisation
7
7-27
GFK-0787B
Chapter 7 Programming Information
Programming for Global Data
In a Series 90-70 PLC/Genius system, Global Data is data that is automatically broadcast
by a PLC bus controller, each bus scan.
by a PLC bus controller, each bus scan.
The GMR software uses this Global Data capability as the vehicle for exchanging system
information between the PLCs. Each PLC provides 8 words of system data to the other PLCs
as Global Data. Because Global Data messages can be up to 64 words in length, up to 56
additional words of Global Data capacity are available for use by the application program.
Since each PLC can broadcast just one Global Data message per bus scan, the system Global
Data and the application Global Data are a sent in the same message.
information between the PLCs. Each PLC provides 8 words of system data to the other PLCs
as Global Data. Because Global Data messages can be up to 64 words in length, up to 56
additional words of Global Data capacity are available for use by the application program.
Since each PLC can broadcast just one Global Data message per bus scan, the system Global
Data and the application Global Data are a sent in the same message.
Global Data for the Application Program
The application program can send Global Data by placing it into %G memory, as
detailed below. Each PLC uses %G0001 through %G0896 to send “application” Global
Data. It is not necessary to use all of the references.
detailed below. Each PLC uses %G0001 through %G0896 to send “application” Global
Data. It is not necessary to use all of the references.
The application program can read Global Data received from the other PLCs from %GA,
%GB, and %GC memory. In addition, each PLC can also read a copy of its own Global Data.
As explained in the PLC chapter of this book, each PLC actually receives two sets of Global
Data from each of the other PLCs. It gives preference to Global Data from the bus designated
bus a. If that data isn’t available, a PLC uses Global Data received from the bus designated
bus b. Under ordinary circumstances, these two sets of data would match. The use of two
busses provides redundant operation in case a bus or bus controller is not available.
%GB, and %GC memory. In addition, each PLC can also read a copy of its own Global Data.
As explained in the PLC chapter of this book, each PLC actually receives two sets of Global
Data from each of the other PLCs. It gives preference to Global Data from the bus designated
bus a. If that data isn’t available, a PLC uses Global Data received from the bus designated
bus b. Under ordinary circumstances, these two sets of data would match. The use of two
busses provides redundant operation in case a bus or bus controller is not available.
The incoming Global Data is data that can be read in %GA, %GB, or %GC memory,
therefore, is the Global Data received on bus a if that data is available. Otherwise, it is
the Global Data received on bus b.
therefore, is the Global Data received on bus a if that data is available. Otherwise, it is
the Global Data received on bus b.
All PLCs
%G0001 –%G0896
Global data to be transmitted.
PLC A
%GA0001–%G A0896
Copy of transmitted global data.
%GB0001–%GB0896
Data received from PLC B
%GC0001–%GC0896
Data received from PLC C
PLC B
%GA0001–%G A0896
Data received from PLC A
%GB0001–%GB0896
Copy of transmitted global data.
%GC0001–%GC0896
Data received from PLC C
PLC C
%GA0001–%G A0896
Data received from PLC A
%GB0001–%GB0896
Data received from PLC B
%GC0001–%GC0896
Copy of transmitted global data.