Behaviour State Lamp

Signal tower and panel-lamp state table

Published from _docs/reference/state-lamp.md — edit it there, not here. Changes made in the wiki are overwritten on the next sync.

The indication contract for H_SignalTower and the H_ControlPanel button lamps: which lamp is on, and whether it is solid or flashing, for every PackML state.

This file is curated, not generated. It once lived under context/, which is the one place it could not survive: that directory is rebuilt wholesale from the twin and anything the build did not write is deleted. It lives here instead, alongside the other hand-written references, where the never-hand-edit rule does not apply.

S — solid colour. F — flashing.

Condition / Indication	Aborting	Clearing	Aborted	Completed	Stopped	Stopping	Resetting	Idle	Starting	Execute	Completing	Holding	Held (No Production)	Unholding	Suspending	Suspended	Unsuspending	Output
Abnormal Stop	F	F	F															Red Lamp Flashing
Controlled Stop				S	S	S	S											Red Lamp Solid
Starved Upstream															F	F		Amber Lamp Flashing
Blocked Downstream															S	S		Amber Lamp Solid
Low Material	F	F	F	F	F	F	F	F	F	F	F			F	F	F	F	Blue Lamp Flashing
Material Exhausted												S	S					Blue Lamp Solid
Ready to Start								F										Green Lamp Flashing
Running									S	S	S			S			S	Green Lamp Solid
Starting / Restarting									F					F			F	Horn
Ready to Start								F										Start Button Flashing
Running									S	S	S			S	S	S	S	Start Button Solid
Ready to Reset			F	F	F													Reset Button Flashing

Reading it against this project

Two translations are needed before this becomes ST, and both are easy to get wrong:

• Completed here is Complete in the PLC. This project runs SPT V3.9, where the state is E_PMLState.ePMLState_Complete; Completed is the V4 spelling and occurs 0 times in the shipped binary. See spt-framework.md.
• The rows are independent conditions, not a priority ladder. Red comes from the state, amber from starvation/blocking, blue from material and green from the state. Two lamps can be lit at once — Low Material is flagged as flashing blue across almost every state, including the ones that also light red or green.

What FG_System implements

Row	Status
Abnormal Stop, Controlled Stop, Ready to Start, Running	implemented — driven from the machine's CurrentState
Start Button Flashing / Solid, Reset Button Flashing	implemented — panel lamp bits, same flash phase
Starved Upstream, Blocked Downstream	input exposed, never TRUE — no starvation or blocking source exists in the machine yet
Low Material, Material Exhausted	input exposed, never TRUE — there is no material model
Horn	not implemented — the twin carries no horn device

The unimplemented rows are present as BOOL inputs on FB_SignalTower defaulting FALSE, so the table can be completed later without touching the lamp logic.

Bit layout

Verified 2026-08-20 against the live PanelSampler._components lists:

Symbol	Bits
H_SignalTower ControlData	0 RED, 1 YELLOW, 2 BLUE, 3 GREEN
H_ControlPanel StatusData (pressed) / ControlData (lamp)	0 START, 1 RESET, 2 STOP, 3 CLEAR, 4 ABORT, 5 PRODUCTION, 6 MAINTANANCE, 7 MANUAL

Note the tower has four lamps, not three, and GREEN is bit 3. The twin's authored prose said three lamps with GREEN at bit 2 until it was corrected on 2026-08-20.

Related

• spt-framework.md — the V3.9 ⇄ V4 differences, including the Complete / Completed split
• ../context/fg-system.md — the devices themselves