ADXL355 external sync


I have same questions about EXT_SYNC=01 Mode of ADXL355.

Could you please advise me  timing specification about the external sync signal? Are there any constraint about the sync signal?

According to the datasheet of ADXL355, EXT_SYNC=01 mode can be used with only a single sync pulse. Can we send only one

sync pulse for synchronization in this case? Or should we send sync pulse continuously?

Best regards,