The AcquiSuite A8812 responds with Error 11: Resource Temporarily Unavailable.
TAC I/A Series
Niagara G3 / R2
The AcquiSuite A8812 internal I/O module (Analog and Pulse inputs) uses Modbus address 250. This is not a legal address for a modbus slave device or ID. Valid Niagara addressing is from address 1 to 247 as stated in the Modbus protocol documentation.
The Acquisuite Obvius LLC company offers a Flex I/O module that can be addressed between 1-247.