PLC / Industrial Networks & PLC Communications
Investigate a one-register Modbus addressing offset
Clients can present addresses as zero-based protocol offsets or one-based documentation references. Mixing them shifts every value.
Environment and inputs: Industrial PLC / automation guidance · Verify the exact controller, module, firmware, engineering tool and machine documentation. Linked vendor examples apply to their stated products and library versions; observation, state changes and physical work require distinct authorization.
Observe and record
Record the device manual's notation and the client software's documented address convention, then compare an approved known read-only register.
Interpret the evidence
A notation such as 40001 is not universally the literal value sent in the protocol address field. Client interfaces vary.
Resolve and verify
Apply the documented conversion once in the managed mapping and validate adjacent documented values and bounds without writing process data.
Machine and data safeguards
Do not discover the map through broad write tests or blindly subtract one from every address across different drivers.