ISA-88 phase hold on permissive loss (graphical LD)¶


suite id	`g_phase_hold_permissive`
domain	chemical_batch
language	LD-graphical
difficulty	medium
validation status	validated
origin	authored
license	CC-BY-4.0

Authored for this suite, modeling an ISA-88 phase HELD state entered on agitator-permissive loss

What is proved¶

From benchmarks/chemical_batch/g_phase_hold_permissive/props.yaml. What each kind claims, and what it becomes on either route, is on The properties we prove.

id	kind	claim	requirement
`P1`	`invariant`	`!(held && heater)`	A phase held on permissive loss must keep the heater off; only clearing HELD through resume_command may re-enable heating.

Variants¶

file	expected verdict	violates	method
`clean.xml`	SAFE	none	expert
`bomb.xml`	VIOLATION	`P1`	fault-injection

Files¶

file	what it is	size	sha256
`benchmark.yml`	benchmark metadata	1.1 KB	`6fae9d3dabb3`
`bomb.xml`	ladder program, PLCopen XML	3.8 KB	`20267edcf036`
`clean.xml`	ladder program, PLCopen XML	3.4 KB	`358665376987`
`props.yaml`	property file	0.2 KB	`13e29f70444b`

Structured text, derived¶

Read off the ladder graph by runner/ld_to_st.py: every rung's contacts and coils rewritten as IEC 61131-3 assignments, in the same series/parallel logic the PLCopen XML encodes. This is a reading aid, not a second source of expected verdicts; ESBMC verifies the ladder program shown above, never this rendering.

bomb.xmlclean.xml

PROGRAM g_phase_hold_permissive_bomb
VAR_INPUT
    run_command : BOOL;
    agitator_ok : BOOL;
    resume_command : BOOL;
    maint : BOOL;
END_VAR

VAR_OUTPUT
    held : BOOL;
    heater : BOOL;
END_VAR


held := ((run_command AND NOT agitator_ok) OR (held AND NOT resume_command));
heater := (((run_command AND NOT held) AND agitator_ok) OR (held AND maint));

END_PROGRAM

PROGRAM g_phase_hold_permissive_clean
VAR_INPUT
    run_command : BOOL;
    agitator_ok : BOOL;
    resume_command : BOOL;
    maint : BOOL;
END_VAR

VAR_OUTPUT
    held : BOOL;
    heater : BOOL;
END_VAR


held := ((run_command AND NOT agitator_ok) OR (held AND NOT resume_command));
heater := ((run_command AND NOT held) AND agitator_ok);

END_PROGRAM

Recorded runs¶

A task can carry two routes. ld is ESBMC's ladder front end reading the program directly. via C is the same solver reached through Beremiz and MatIEC, which is the only route that reaches ST, IL, FBD and SFC; see How ESBMC-PLC works.

g_phase_hold_permissive__bomb (props.yaml, expected VIOLATION): v8.4 VIOLATION
g_phase_hold_permissive__clean (props.yaml, expected SAFE): v8.4 SAFE