Data communication system and data communication apparatus

A data communication system that performs data communication between a master station and a plurality of slave stations in a token passing system employing an Ethernet (registered trademark), wherein

• the master station includes:
• a communication processing unit that performs, as first data transmission and reception processing, data transmission and reception between the master station and the slave stations performed by circulating a token frame between the master station and the slave stations;
• and
• a data transmission and reception processing unit that is connected to an arithmetic processing device and performs, as second data transmission and reception processing, data transmission and reception performed between the arithmetic processing device and the communication processing unit, the arithmetic processing device subjecting data transmitted from the slave station to arithmetic processing and generating data transmitted to the slave station, and
• the communication processing unit performs, as third data transmission and reception processing, data transmission and reception performed between the communication processing unit and the data transmission and reception processing unit and, when the first data transmission and reception processing is performed, repeatedly transmits the token frame to a data transmission and reception target slave station a plurality of times.

A data communication apparatus serving as a master station that performs data communication between the data communication apparatus and a plurality of slave stations in a token passing system employing an Ethernet (registered trademark),

• the data communication apparatus comprising:
• a communication processing unit that performs, as first data transmission and reception processing, data transmission and reception between the master station and the slave stations performed by circulating a token frame between the master station and the slave stations;
• and
• a data transmission and reception processing unit that is connected to an arithmetic processing device and performs, as second data transmission and reception processing, data transmission and reception performed between the arithmetic processing device and the communication processing unit, the arithmetic processing device subjecting data transmitted from the slave station to arithmetic processing and generating data transmitted to the slave station, wherein
• the communication processing unit performs, as third data transmission and reception processing, data transmission and reception performed between the communication processing unit and the data transmission and reception processing unit and, when data reception processing for circulating the token frame between the master station and the slave stations and receiving the data from the slave stations in the first data transmission and reception processing is subjected to retry processing, after performing the first data transmission and reception processing, circulates the token frame between the master station and the slave stations and receives the data from the slave stations without performing the third data transmission and reception processing to thereby subject the processing to the retry processing, and performs the third data transmission and reception processing after the retry processing.

A data communication apparatus serving as a master station that performs data communication between the data communication apparatus and a plurality of slave stations in a token passing system employing an Ethernet (registered trademark),

• the data communication apparatus comprising:
• a communication processing unit that performs, as first data transmission and reception processing, data transmission and reception between the master station and the slave stations performed by circulating a token frame between the master station and the slave stations;
• and
• a data transmission and reception processing unit that is connected to an arithmetic processing device and performs, as second data transmission and reception processing, data transmission and reception performed between the arithmetic processing device and the communication processing unit, the arithmetic processing device subjecting data transmitted from the slave station to arithmetic processing and generating data transmitted to the slave station, wherein
• the communication processing unit performs, as third data transmission and reception processing, data transmission and reception performed between the communication processing unit and the data transmission and reception processing unit and, when the first data transmission and reception processing is performed, repeatedly transmits the token frame to a data transmission and reception target slave station a plurality of times.