can two of 8313 cpus run synchronously？

[arthurma]

we made a board within two 8313 cpus.

the cpus have the same power, same Crystal Oscillator and same reset signal.

we run the same firmware in the two cpus.

we expected the cpus run synchronously and don't be different more than 200ns. but they don't.

we want to know whether and how can do it?

[r8070z]

Have a great day,

For sure if firmware test or wait for anything or there is external interrupts, then even identical MPC8313 sourced from the same clock may not run synchronously.

Did you try use the same SRESET for both MPC8313 while all its peripherals have been initialized to the same states?

How do you estimate the difference in 200 nanoseconds?

[arthurma]

   thanks for you reply.

  we have to let the two cpus read the same fpga, and the fpga can wait when it found the two cpus did not read in same time. but the time of fpga wait we set is not great than 200ns. this time can be set greater, but we don't want to do this now.

  we caught timing sequence through fpga by singletap. we found the two cpus may run differnt after read DDR some times.

   so we thought it is imposible  to make two cpu run synchronously. because we can't make cpu read DDR in same timing sequence. 

   another project use similar design, but they use other type cpu and use sram for ram while using wait signle in localbus  to synchronize.

  so we may be have to change our design.