LadderLens — OT workspace · P&ID, controllers & live logic

editing

Structured text

examples

Inputs

Outputs this scan

Diagram

bit timers & counters compare math

[ ] normally open — passes power when TRUE · [/] normally closed — passes power when FALSE
series contacts are AND · parallel branches are OR · +∥ adds a branch · wires light where power actually flows
green = energized this scan · arithmetic uses function blocks, not operators
an IF/ELSE in text becomes two rungs gated by the same variable and its complement

the diagram is editable: click a tag, pin, or coil to rename it · click a contact symbol to flip [ ]/[/] · drag ⋮⋮ to reorder rungs · drag contacts to reorder them · × deletes · type any expression into a pin
diagram edits regenerate the text in flat rung form — complementary rungs collapse back to IF/ELSE, comments are dropped

this is a real scan: state persists between scans, so seal-in rungs latch and TON/TOF/TP timers, CTU/CTD counters and R_TRIG/F_TRIG edges work — declare instances in VAR … END_VAR, call them like tmr(IN := b, PT := T#5s), read tmr.Q · reset is a cold restart · step single-scans while stopped

view layers process signals examples drag a device to move it · drag the background to pan · ctrl + wheel to zoom · double-click a controller to open its logic

Device

click a device to configure it — drag to move

Live tags

no bound tags

how the plant runs

the plant runs on the same scan as the logic: transmitters write their tank's level into their tag before each scan, the logic runs, then valves and pumps move flow and tanks integrate it

valve opens to its tag's value (0–100) — with a position tag it draws as an automated valve, without one it is a hand valve at a constant opening · pump runs from a BOOL tag · LT publishes tank level · FT publishes the flow through a valve or pump · LSH/LSL publishes TRUE when its tank crosses the trip point — wire it into an interlock · flows animate where liquid moves · a full tank with net inflow shows overflow

controllers declare a make and model from the device catalog — identity today, and the anchor for vendor dialect translation on the roadmap

a controller is a device too: select it and press open logic (or double-click it) to edit the program it runs · the Logic view shows which program you are editing — a controller's, or the free-standing sandbox

try the level control plant, watch it settle near SP — then load the sign error logic example and watch the same plant run away · the workspace is saved in this browser and travels as a .llp project file; a .st file carries logic alone

every device from the P&ID appears in its level · drag a card between lanes · link two devices to draw a conduit · click a conduit to set its traffic · double-click a controller to open its logic

Placement & traffic

click a device to place it in a level, or a conduit to configure its traffic

Segmentation review

about the Purdue model

the Purdue model (ISA-95) is how OT networks are drawn: the process at the bottom, business systems at the top, and progressively less trust as you go up

Level 0 field instruments and final elements · Level 1 controllers · Level 2 HMI and engineering workstations · Level 3 operations, historians · DMZ the broker that lets IT and OT exchange data without touching · Level 4 the business network

this is the same project you drew on the P&ID — a tank in Level 0 here is the tank on the P&ID, and a controller you place in Level 1 is the one running your logic

a firewall is a device on a conduit, the way a valve sits in a pipe — click it to set which protocols it permits, and watch denied packets stop at it

traffic runs on the scan clock: HMIs, workstations and historians poll the controllers they are linked to; a request travels out and a reply comes back carrying a live tag value. Click a conduit to set its protocol, poll rate, and which tag it reads

the segmentation review flags what an assessor would write up: traffic that skips levels, control protocols crossing the DMZ, enterprise systems reaching into the plant