Hi Paul -
The oscillators for the CGM modules on HC08's were only designed for the 1 - 8MHz crystal range.
If you look at the Data Sheet in the General Description section:
"* Clock generation module supporting 1-MHz to 8-MHz crystals"
Then, back in the Electrical Characteristics in the 5.0-Volt Control Timing table it has under Frequency of operation that the crystal option is 1 to 8 MHz while the external clock option is dc to 32 MHz. So you can have up to a 32MHz external clock, but it means that you have to feed an externally generated square wave into the OSC1 pin.
- Rocky
If the system clock is generated from a PLL, it is recommended to select the crystal clock source rather than the system clock source due to jitter considerations, especially at faster CAN bus rates.
Rocky, can you clarify that last statement? 'We don't recommend using the PLL on any of the current parts.'
Do you mean with the CAN or with the internal clock or not at all?
Does the CAN receiver resynchronize its clock with signal transitions? I know the CAN specification includes bit stuffing for that reason.
Sorry that I wasn't clear. I did mean that we don't recommend using the PLL as the clock for the MSCAN module.
As I say, I'm not an expert on CAN. I did check with our CAN expert in the group and he confirmed that the current crop of PLL's on our parts do not provide the accuracy because of jitter for CAN.
- Rocky