Patent ID: 8762582

Claim:
A data processing apparatus comprising: a data processing unit configured to process data; a communication unit configured to communicate with an external device via at least two logical lines including a first logical line and a second logical line, the second logical line having a higher priority than the first logical line; a storage unit including a first buffer area for storing data that is received by the communication unit via the first logical line and a second buffer area for storing data that is received by the communication unit via the second logical line; and a control unit configured to: determine whether the second buffer area stores data; read data from the second buffer area, control the data processing unit to process the data read from the second buffer area, and transmit a reception waiting notification to the external device via the first logical line, in response to a determination result indicating that the second buffer area stores data; transmit a reception waiting cancel notification to the external device via the first logical line on completion of the processing of the data stored in the second buffer area; and determine whether the first buffer area stores data, in response to a determination result indicating that the second buffer does not store data.