S7-1500 watchdog after a TIA V19 download — cell stays in STOP

SiemensField note

The question

Press shop, S7-1500, TIA Portal V19. After a small OB1 edit the CPU comes up then drops to STOP with a diagnostic buffer pointing at a cycle watchdog. No new hardware. Anyone seen this on a Comfort Panel HMI that still talks V17 tags?

TS ControlsThe answer

Check the HMI connection resources and any cyclic WinCC script you added in V19. We had a tag group set to 10 ms that ate the scan. Bump the cycle watchdog in the CPU properties only after you find the extra traffic — don't just raise it and walk away.

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