Minimum Amplitude of the External Clock Input

[jiunnyang]

As we know the PB is 5V system MCU, and the SU is also high operating voltage(4.5~18v).

How minimum amplitude of the external clock input for the MC9S08PB8VTG and MC9S08SU8?

is there okay for 3.3v OSC?

I can not find these parameters in Datasheet.

Thanks!

[xuan_wu]

Hi Jiunn,

You can find these parameters in the table: DC characteristics in S08PB/S08SU datasheet.

As shown in the above table, the minimum amplitude of external clock input can be calculated by the marked formula.

1. The voltage: Vddx = 5V,  the minimum high voltage of the pin: 0.70 x 5v = 3.5V,   3.3V OSC is not OK.

2. The 3.3V OSC is ok only if Vddx <=4.7V.

Thanks