How to ensure signals from multiple different clocks are in phase?
exactly per jwh20 in the comments:
Use a counter aka frequency divider (wiki link, see &quot;digital dividers&quot; section), from the common clock. You can divide by any positive integer value, not just powers of two. Look up &quot;counter&quot; IC's. If you are in a microcontroller, the same can be done with common on-chip timer/counter hardware.
With a ratio of 10e6 you will need 24 bits, if for any reason you are forced to use something with fewer bits, you can use multiple counter/dividers with fewer bits in series.
HOWEVER! as I overlooked, to get the 1Hz outputs in phase, a common trigger would be required to start the counting, which makes the benefit unclear.