The DS89C450 is pin and functionally compatible with the DS89C440. Designs using the DS89C440 should upgrade to the DS89C450. Software compatibility must be verified in the upgrade process. The DS89C440 has two 16KB banks of FLASH, while the DS89C450 has two 32KB banks of FLASH. If your application code is dependant on the bank size being 16KB, it will need to be modified to work on the DS89C450.
The Ultra-High-Speed Flash Microcontroller User's Guide should be
used in conjunction with this data sheet.
Download it at www.maxim-ic.com/microcontrollers.