Epiphany Timers Synchronization

Hi,
I wonder how to synchronize the timers in all cores? for example i want to start e_ctimer0 in all cores at the same time the purpose of this is to get the travel time for read and write transactions.
I wonder how to synchronize the timers in all cores? for example i want to start e_ctimer0 in all cores at the same time the purpose of this is to get the travel time for read and write transactions.