The MPC8309 Reference Manual (Rev. 2) section 18.104.22.168, System PLL Mode Register (SPMR) states:
It obtains its values according to the reset configuration input signal and
the reset configuration word low loaded during the reset flow. Note that this register is updated only during
a power-on reset sequence and not by a hard reset sequence. It may hold values different than those in the
RCWLR after a a hard reset sequence.
The register is also documented as being read-only.
Please clarify how the register is (re-)initialised after a hardware reset. Under what circumstances might it have values different to those in the RCWLR, and what is the impact of any such changes?