Hi,
There are some differences in the naming convensions between the 5282 and 5213. The SYNCA and SYNCB pins are actually for ADC of the 5213. These are external timer clock inputs to trigger ADC conversions.
The GPT on 5282 has SYNC inputs that reset the free-running counter. This functionality was not implemented on 5213. Unfortunately, it looks like an old documentation note snuck in the 5213 manual (Table 18-2). I can put in a request to have it updated.
Thanks for your feedback. If you encounter any more documentation errors, please submit a service request.
Thanks,
Mac