A vehicle-mounted communication control apparatus includes: microprocessor
110a to which serial-parallel converter 117 for master station is
connected; and common control circuit 120a to which serial-parallel
converter 127 for substation is serial-connected to serial-parallel
converter 117. The control apparatus includes first storage device 300 for
storing transmission from master station to substation; distribution
storage device 313 for transferring command data to device memory when
command data stored in first storage device 300 is write/setting command;
reply packet generation device 317 for generating up-reply information to
microprocessor 110a; second storage device 320 for reading out on the
principle of preceding input or preceding output while storing in order
reply information and evacuating the delay; and reply packet composing
device 338 for adding latest information to reply information and sending
back resultant reply information.
