Modbus TCP
What the SCADA connects to
Point the Mini SCADA at this unit’s IP on this port.
Register layout
| Range | Contents |
|---|---|
| Registers 0–511 | Polled word data |
| Coils 0–511 | Polled bit data |
| — | Gateway health — reserved, never allocated to a block |
Polled data starts at register 0, so a SCADA address matches the PLC’s own index and the gateway reads as transparent. Park the diagnostics at 480 and forget about them, or put them immediately after your polled range.
Mind the collision: a block cannot straddle the diagnostic area. Set it to 24 and you have exactly 24 registers of polled data. The unit refuses an overlapping block rather than letting the two fight.
Mind the collision: a block cannot straddle the diagnostic area. Set it to 24 and you have exactly 24 registers of polled data. The unit refuses an overlapping block rather than letting the two fight.
Health registers worth alarming on
| Register | Meaning |
|---|
Coils at the same base carry the unit’s own I/O: +8–11 are digital inputs IN1–IN4, +12–15 are relay states R1–R4 (read-only — the diagnostics and the alarm engine drive those, so the SCADA can watch them but not fight for them).
The bold number is the absolute register the SCADA reads; (+n) is the offset within the block. They match only when the diagnostics address is 0 — at the default 480 the first row reads 480 (+0).
A gateway quietly serving stale data is this product’s classic failure. These are the cheap defence: alarm on them in the SCADA and a dead bus announces itself instead of looking like a process that simply stopped changing.