A fixed SNPA prefix for use when the ciiRAMapType is
extractDSP. The SNPA Address to use is formed by
concatenating the fixed SNPA prefix with a variable SNPA
part that is extracted from the effective destination
address. For Reachable Address prefixes in which the
entire SNPA is embedded in the DSP the SNPA Prefix shall
be null. This object follows the ManualOrAutomatic
behavior.