This section describes the function and parameters for module timeout and module ownership registers.

The module timeout register specifies the amount of time that outputs will be held in their current state, if they are not updated by a new Modbus Plus Write command. If the module's holdup time expires before a new write command is received, all outputs are set to logical 0 (zero).

Module ownership registers specify the addresses of up to three nodes which may concurrently own write privilege to the adapter.

When the adapter first receives power, it will give sole write privilege to the first node that writes to it. The adapter maintains an internal 60-second timer for handling the write privilege, and will reserve sole privilege to that node as long at the node continues to write within 60-second intervals to the adapter.

A node which currently owns the write privilege may write up to three words to the adapter starting at reference 4F401. Each of the three words must correspond to a valid node address in the range 1...64 decimal. With those addresses stored in the adapter, any of those three nodes may then write to the adapter. This allows up to three nodes to concurrently own write privilege to the adapter.

If writes continue to occur within the 60-second interval from any of the three privileged nodes, no other node may write to the adapter. If the timer is allowed to expire, any node may write to the adapter.

Note that this 60-second Write Privilege timer is separate from the Outputs Holdup timer, and applies only to the write privilege. Any node may read the input data or status information from the adapter. The 60-second time is a fixed value and is not accessible to the application.