NMRA CV 11 - Packet Time-Out Value
This CV sets up the maximum time period that the decoder will maintain its speed without receiving a valid DCC packet.
From NMRA Standard S-9.2.4 Section C:
"While in digital operations mode if the packet time-out value is exceeded the Multi Function Digital Decoder will bring to a stop all controlled devices. The purpose of this time-out is to insure that each Multi Function Digital Decoder receives a periodic update from the Digital Command Station and thereby help prevent runaway conditions. The user should be able to define the value for this time-out within these restrictions:
A value of 0 disables the time-out (i.e., the user has chosen not to have a time-out). A value range of 1 through TIMEOUT_MAX sets the time-out to the chosen value. The minimum value of TIMEOUT_MAX will be 20 seconds. It may be longer at the manufacturer's discretion."'