Learn Modbus the way integrators actually use it.

The mental model, why Modbus is still everywhere, and what it deliberately does not give you.

PDU vs ADU, how requests, responses, and exceptions actually look on the wire.

Coils, discrete inputs, input registers, and holding registers — the four primitives.

Reads, writes, diagnostics, and the codes you'll actually meet in the field.

0-based wire addresses vs 1-based documentation, and how off-by-one bugs are born.

Reading a vendor map and turning it into a reliable, reviewed integration plan.

INT16, UINT16, INT32, FLOAT, word/byte order, and the encoding traps you'll hit.

Raw register → engineering value with units, scale, and a sanity check at every step.

Baud, parity, stop bits, timing — the fundamentals every RTU integrator must own.

Topologies, biasing, termination, and why your bus quietly stops working at node 17.

Frame structure, CRC vs LRC, silent intervals, and reading captures by hand.

MBAP, unit identifiers, ports, and what changes (and doesn't) moving from RTU.

TCP↔RTU routing, unit IDs, latency, and how to keep mixed deployments diagnosable.

A repeatable evidence-first method for diagnosing failed reads, writes, and timeouts.

What classic Modbus does not protect, write safety practice, and TLS / Modbus Security.

Bring a real or simulated device online with a reviewable evidence package.