A delay time period, such as the H/W process time period, and the S/W
process time period needed for starting up a timer, and a time period from
the task starting to the packet transmission beginning are predicted and
stored in the control information in advance. A set value calculating part
calculates a timer set value at the system initialization. In a packet
forming part, the timer set value is set in a relative time timer for
starting the timer. The relative time timer generates an interrupt after a
specific elapse time has passed for starting a transmission requesting
part. By dint of this, the time lag of the time period from the period
interrupt to the packet transmission beginning can be reduced, and each of
the formed packets is certainly requested to be transmitted within each
requested time period for processing.
