Patent ID: 7062579

Claim:
A data transmission method for devices connected by a serial bus, said method comprising the steps of: locking communication of a receiving device that receives a data transfer from a transmitting device using a locking transaction of an IEEE 1394 transaction layer, prior to the data transfer; reading processing capability information indicative of a data processing capability of the receiving device, said reading being performed by the transmitting device using a read transaction of the IEEE 1394 transaction layer, prior to the data transfer; determining a data block size used in data communication by the transmitting device, in accordance with the read processing capability information; and transmitting the data in the determined data block size from the transmitting device to the receiving device, said transmitting being performed by the transmitting device using a write transaction of the IEEE 1394 transaction layer, wherein the processing capability information indicates a capability of the data communication in which data block transfer is performed and is notified via the IEEE 1394 transaction layer.