Job-readiness and assessment field guide
CCST 004 TOF off-delay timer practice: readiness checklist
Direct answer
The candidate can predict a TOF timing diagram, test true-to-false and false-to-true transitions and diagnose unexpected retained or reset behavior.
Written for controls candidates learning how an off-delay instruction differs from on-delay timing and how platform details affect observed state.
Role scope
Enable condition, preset, time base, elapsed or accumulator state, timing state, done state, output use, scan interval and restart semantics.
Skills map
Input transition through timer instance and scan execution into status values, downstream logic, output command and physical response.
Core exercise
Enabled, falling-edge timing, expiry and re-enable transitions matching a written timing diagram over repeated scans.
Stretch case
Zero preset, re-enable before expiry, changing preset, scan jitter, duplicated timer instance, controller stop, restart and retained state.
Troubleshooting
An enable, transition, instance, preset, time-base, scan, status-bit, downstream or restart mismatch.
Portfolio evidence
The timing cases recreated using exact target-platform help and verified against the intended task and output behavior.
What does a TOF timer do?
An off-delay timer commonly keeps its done condition true for the preset period after the enabling condition becomes false, but exact status and restart behavior are platform-specific.
What happens if a TOF input turns true again while timing?
Many implementations stop the off-delay and restore the enabled state, but verify the exact instruction definition and include that transition in the test table.