Patent ID: 8184314

Claim:
An image forming apparatus, comprising: a main body having a main controller controlling the image forming apparatus to output an image; at least one optional tray which is detachably set up in the main body and has a tray controller for communicating with the main controller to transmit and receive data; and communication lines that form one communication channel connecting the main controller and each tray controller, make the main controller and the tray controller exchange the data, and inform the main controller that the data is provided from at least one tray controller to the main controller, wherein the communication lines include a TXD line providing data from the main controller to each tray controller, an RXD line providing data from the tray controller to the main controller, and a busy line informing that the data is provided from at least one tray controller to the main controller through the RXD line, and the TXD line, the RXD line, and the busy line are separate from each other.