MC9S12HY64 Datasheet, PDF (133/792 Pages) Freescale Semiconductor, Inc – S12 Microcontrollers

2.5 Initialization Information
Port Integration Module (S12HYPIMV1)
2.5.1 Port Data and Data Direction Register writes
It is not recommended to write PORTx/PTx and DDRx in a word access. When changing the register pins
from inputs to outputs, the data may have extra transitions during the write access. Initialize the port data
register before enabling the outputs.
MC9S12HY/HA-Family Reference Manual, Rev. 1.04
Freescale Semiconductor
133