Allen-Bradley PLC-5 User Manual page 138

9-6 Communicating with Devices on a DH+ Link
The Global Status Flag data for each node address on your DH+ link is stored in the word address
corresponding to the octal node address. For example, if your DH+ link has processors at node addresses
7, 10, 15, and 30 and your global status flag file is N10 for each processor, the global status flag data is
stored as follows:
DH+ link
Station 7
Global Status Flag File
defined in each
processor: N10
Decimal: N10:7
Octal: N10:7
You can specify any integer file in the processor to be the global status flag file; however, for simplicity,
specify the same file for all your PLC-5 processors on the DH+ link.
The files are updated during housekeeping.
Publication 1785-UM012D-EN-P - July 2005
This process lets each station automatically see the newly updated data. You
can create ladder logic to monitor and interpret this data according to your
application.
Station 10
Decimal: N10:8
Octal: N10:10
Make sure that the global status flag file in all of the controllers on your DH+
link is as large as the highest node address, so that all of the nodes can
communicate with each other. If station 30 is the highest node number, for
example, the global status flag file (N10) in each controller must be 24 words
long (octal 30 = decimal 24). When you first configure the global status file, it
automatically gets 64 words.
Do not allow either external or internal messages to write
IMPORTANT
into the global status flag file. Writing into the global status
file faults the controller.
You can change the radix in the data monitor to display the file address in octal
so that you can see the element number of the octal address matching the node
address.
Station 15
Decimal: N10:13 Decimal: N10:24
Octal: N10:15 Octal: N10:30
Station 30