For fixed and tunable Clocks, the interval either depends on fixed/tunable parameters or can be set by the importer. In the first case, the attribute intervalDecimal must not be defined for fixed/tunable Clocks in the model description.

Fixed Clocks:

If intervalDecimal is not specified, then the importer must use fmi3GetInterval and fmi3GetShift to retrieve the Clock interval and shift in Initialization Mode because they depend on fixed parameters.

Tunable Clocks:

If intervalDecimal is not specified, then the importer must use fmi3GetInterval to retrieve the Clock interval in Initialization Mode, and later in Event Mode or Clock Activation Mode, if any of the tunable parameters the Clock’s interval depends on was changed. The shift may only depend on fixed parameters. The importer must use fmi3GetShift to retrieve the Clock shift in Initialization Mode.

However, the description of intervalDecimal says:

This attribute is required if Clock type is constant, fixed or tunable periodic Clocks. It must not be used otherwise.