Panasonic FP0R User Manual page 168

LD Body
NOTE
 The setting should not be changed as long as a longer transmission
assurance relay detection time does not cause any problems.
 The SYS1 instruction should be executed at the beginning of the program,
at the rise of R9014. The same waiting time should be set for all linked
PLCs.
 The time should be set to a value of at least twice the maximum
transmission cycle time when all of the PLCs are connected to the link.
 If a short time has been set, the transmission assurance relay may not
function properly. (The shortest time that can be set is 100ms.)
Communication
167