01
Runs the real program
The controller's own program runs scan by scan with that PLC's behaviour: timers, counters, edges and data types, just as the CPU would run it.
Product in development
AIS SoftPLC: a PLC in software, so we can test before we touch the machine.
We use the AIS SoftPLC for simulation. It runs a real controller program on a PC, scan by scan, wired to a simulator of the machine, and it answers the network like the real CPU. So far it simulates a Mitsubishi MELSEC iQ-R R08CPU and a Sharp PLC.
Developing
What it does
The program, the PLC and the machine, all on one PC.
Most of the machines we work on can't be stopped for testing, and some can't be tested on hardware at all. The SoftPLC means our code has already run, and passed, before it gets anywhere near your line.
02
Answers like the real CPU
HMIs, OPC servers, SCADA and data-collection devices connect over SLMP as if it were the real PLC, including label access by name. Tested with 80 simultaneous clients and 20,000 malformed frames.
03
Wired to a machine simulator
Inputs and outputs connect to a model of the machine, so sensors change, motors run and parts move when the program tells them to. Faults can be injected on purpose.
04
Scripted test scenarios
Timed steps set inputs, wait and check results, with checks on every scan. The same scenarios run again after every change, so nothing that worked gets broken.
05
Restart sweep
The machine is stopped at 60 points in a cycle and at a fault, and each time restarted with retained memory. Deliberate program faults check that the tests catch them. On a relay-style PLC it found a stray counter pulse on the restart scan of a new sequence before it reached the machine.
Status · 29 October 2026
What runs today, and what is coming.
A PLC stores instruction codes, not drawings. The SoftPLC runs that instruction list with each family's own behaviour on one engine, and each PLC family is a profile on top: its memory model, its instructions, its special relays and its protocol. A comparison with a real CPU comes before we call anything verified.
In use
On AIS projects; byte-exact against the manuals.
- The instruction-list scan engine
- SLMP server: 3E / 4E, binary and ASCII, TCP and UDP, device access and labels by name; AIS Edge and AIS HMI connect to it
- Sharp JW profile: scan behaviour, octal devices, keep area, special relays
- Machine models, scenario tests, the restart sweep and the local web panel
In testing
Passing in simulation; comparison with real hardware pending.
- MELSEC iQ-R profile: device memory, timers and counters, edges
- Remote RUN / STOP / RESET, and an exact mode with the CPU's own limits and error codes
- Next: a byte comparison against a real iQ-R CPU, and third-party OPC servers and SCADA on our lab network
In development
Being built now, or next on the list.
- All five IEC 61131-3 languages: ladder (LD), function block diagram (FBD), structured text (ST), sequential function chart (SFC) and instruction list (IL), with function block instances
- Loading GX Works3 programs with labels, function blocks and SFC
- EtherCAT®, CC-Link IE and TSN stations through AIS Core, the protocol engine shared with AIS Edge
IEC 61131-3 · in development
Every IEC 61131-3 language, on one engine.
Ladder, function block diagram, structured text, sequential function chart and instruction list will all compile to one instruction list, so a mixed program runs in one scan with one memory. Full IEC 61131-3 support is in development; the instruction-list engine under it runs today.
- Ladder (LD). Today ladder programs run from their instruction list, for the MELSEC and Sharp JW profiles, and show live in the AIS HMI ladder monitor
- Function block diagram (FBD). Function block instances, the standard blocks (TON, TOF, TP, CTU, CTD, R_TRIG, SR, RS) and the standard functions
- Structured text (ST). In the same scan as ladder; a first ST compiler already drives a production scheduler in simulation and is being moved into the SoftPLC
- Sequential function chart (SFC). Steps, transitions, actions in ladder or ST, and checks on every scan that exactly the expected steps are active
- Instruction list (IL). The engine's own form; unknown instructions are refused, never ignored
Simulating so far
Two PLC families today, more on the way.
Mitsubishi MELSEC iQ-R
- R08CPU
- SLMP 3E and 4E frames, binary and ASCII, TCP and UDP
- Label access by name
- Remote RUN / STOP
Sharp PLC
- Sharp JW-series program behaviour: scan, octal devices, keep area, special relays
- Used to prove a new automatic test cycle in simulation before it reached the machine
What we use it for
Proving the code, not hoping.
- Testing program changes and new logic before they go to the machine
- Building and testing HMI and SCADA screens against a live-behaving PLC
- Checking data collection and OPC setups without plant hardware
- Reproducing a fault in simulation to test a hypothesis
- Training people on a machine without risking the machine
Protocols
What the SoftPLC speaks today, and what's next.
The SoftPLC is the PLC, so it serves the server or device side of each protocol. Our Edge Device builds the client side, and each one is the other's test partner.
Running now
| Protocol | PLC family | Status |
|---|---|---|
| SLMP / MC protocol, 3E and 4E framesbinary and ASCII, TCP and UDP, label access by name | Mitsubishi MELSEC iQ-R, Q, L, iQ-F | In use byte-exact to the SLMP manual; real-CPU comparison next |
Roadmap: featured, through AIS Core
| Protocol | SoftPLC role | Status |
|---|---|---|
| EtherCAT® | Simulated segment (master and devices from ESI files), then device emulation on a real network port | Planned |
| EtherCAT TSN | Stream adaptation; EtherCAT Automation Protocol over TSN | Planned |
| Ethernet TSNIEEE 802.1AS time sync, 802.1Qbv scheduled traffic, launch times | TSN station on a real-time host | Planned |
| OPC UA PubSub over TSN | Publisher and subscriber | After TSN |
| CC-Link IE TSN, CC-Link IE Field Basic | Station | Planned |
These come from AIS Core, the protocol engine shared with AIS Edge. Its EtherCAT master (with eight simulated devices) and its CC-Link IE and TSN stacks are in testing in AIS Edge, in simulation, with a Python binding the SoftPLC will embed. AIS is a member of the EtherCAT Technology Group (ETG) and the CC-Link Partner Association (CLPA). EtherCAT® is a registered trademark and patented technology, licensed by Beckhoff Automation GmbH, Germany.
Roadmap: open protocols (any PLC family)
| Protocol | SoftPLC role | Status |
|---|---|---|
| Modbus TCP, Modbus RTU / ASCII | Server / slave | Early |
| OPC UA | Server, unsecured first, then signed and encrypted | Early |
| MQTT 3.1.1 / 5.0 with Sparkplug B | Edge-of-network node | Planned |
| EtherNet/IP (CIP) | Adapter | On request |
| PROFINET IO | Device | On request |
| BACnet/IP, DNP3, IEC 60870-5-104, IEC 61850 | Server / outstation | On request |
| SECS/GEM (HSMS) | Equipment side | On request |
Roadmap: vendor protocols (with each PLC family)
| Protocol | PLC family | Status |
|---|---|---|
| MC protocol 1E | Mitsubishi FX3U Ethernet, A-compatible | Planned |
| Sharp JW computer link | Sharp JW | Planned |
| Omron FINS | Omron CS / CJ / NJ / NX | Planned |
| Beckhoff ADS | TwinCAT 2 / 3 | Planned |
| Panasonic MEWTOCOL-COM | FP7, FP0H, FP-XH | Planned |
| LS ELECTRIC XGT FEnet | XGK, XGI, XGB | Planned |
| YOKOGAWA FA-M3 PC link | FA-M3 | Planned |
| KEYENCE KV Host Link | KV-8000 / 7000 / 5000 | Planned |
| FATEK FBs, Unitronics PCOM, Opto 22 OptoMMP | FATEK, Unitronics, Opto 22 | Planned |
Every protocol is built from its published specification. Where a protocol has a conformance program, we claim it in the product only after passing it. Siemens controllers are covered through OPC UA. The order may change with customer demand.
Want your machine simulated?
If you have a change to make on a machine you can't afford to stop, we can usually build a simulator of it first. Tell us what it is.