To switch the decoder into Test Mode, the host sends

STOPOPERATION<CrLf>

The decoder responds with:
If the operation mode was stopped:

STOPOPERATION;OK<CrLf>

If the decoder already was in Test Mode:

STOPOPERATION;TESTMODE<CrLf>

Example

← STOPOPERATION<CrLf>
→ STOPOPERATION;OK<CrLf>