RTEMS Porting Guide
The _Priority_Bit_map_Control type is the fundamental data type of the
priority bit map array used to determine which priorities have ready
tasks. This type may be either 16 or 32 bits wide although only the 16
least significant bits will be used. The data type is based upon what is
the most efficient type for this CPU to manipulate. For example, some
CPUs have bit scan instructions that only operate on a particular size of
data. In this case, this type will probably be defined to work with this
instruction.
RTEMS Porting Guide
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