The DG128B is a legacy device and not recommended for new design. MC9S12DG128CPV & MC9S12DG128BCPV pinouts and HW are 100% compatible.The pins have the same connection and placement. They use the same HW blocks and memory map. However, the DG128 and DG128B have different silicon masksets. The new DG128 has some enhancements and there are differences in errata too. Customers may have to slightly modify their old software to work correctly on the new DG128 devices.
See Silicon Mask set Errata for DG128 devices for details available on our website. There you can see which HW modules may be affected (depending on your silicon maskset) The silicon maskset is marked on the chip package. Please compare the errata for your current DG128 mask and the old DG128B mask and focus on HW blocks that you use in your SW application Links for the Errata.
The one of main difference between DG128B and DG128 is in NVM reliability (Flash data retention) (Different Flash technology)
Regards,
Nina