MC9S12ZVC has a on-chip voltage regulator with ballast pins BCTL and BCTLC which supply base current to the ballast transistor to get VDDX, VDDA and VDDC. The reference design uses a 5.6V zener diode at the VDDX and VDDA but the data sheet says it is a 5V input. If they are generated by the on-chip regulator why use a 5.6V zener at VDDX and VDDA? I have attached the screenshot of the schematic below.
Please Advice.Thank you!