Bradley Smoker PLC-5 user manual 6Communicating with Devices on a DH+ Link

9-6Communicating with Devices on a DH+ Link

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.

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

Station 10

Station 15

Station 30

Global Status Flag File defined in each processor: N10

Decimal: N10:7	Decimal: N10:8	Decimal: N10:13	Decimal: N10:24
Octal: N10:7	Octal: N10:10	Octal: N10:15	Octal: N10:30

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.

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.

IMPORTANT

Do not allow either external or internal messages to write 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.

Publication 1785-UM012D-EN-P - July 2005