Patent ID: 8576704

Claim:
A communication system including a first communication device and a plurality of second communication devices, the first communication device and the second communication devices being connected with one another in a ring via a serial link, wherein the first communication device comprises: a first command processing unit configured to, when a downlink is not used for data packet transfer, issue a standby packet to a partner device that is one of the second communication devices with which the first communication device performs communication, the downlink being a part of the serial link extending from the first communication device to the partner device; and a first data transfer unit configured to (i) transmit a write data packet to be written via the downlink, and (ii) receive a read data packet to be read via an uplink, which is a part of the serial link extending from the partner device to the first communication device, and each of the second communication devices comprises: a second command processing unit configured to, when the uplink is not used for the data packet transfer and a respective one of the second communication devices is the partner device, issue the standby packet to the first communication device; a second data transfer unit configured to receive the write data packet via the downlink and transmit the read data packet via the uplink; a packet relay unit configured to, in accordance with a destination of a packet input to a respective one of the second communication devices, relay the input packet to one of the first and second communication devices that immediately succeeds a respective one of the second communication devices in the ring; and a standby control unit configured to, when the input packet relayed by the packet relay unit of a respective one of the second communication devices is the standby packet, cause a respective one of the second communication devices to switch to standby mode.