Image forming apparatus and communication data handling method therein

An image forming apparatus comprising a unit and a controller which controls the unit, and in the image forming apparatus, only after a command is sent from the controller, verifying a proper response is sent from the unit side for the command, wherein

• said controller comprises,
• a response detecting means which detects a receipt of a response from said unit side, and
• a transmission stop means which stops sending the command when the receipt of said response is detected by said response detecting means during transmission of said command.

A communication data handling method in an image forming apparatus comprising a unit and a controller which controls the unit, and the apparatus performing data sending and receiving between the unit and the controller, wherein,

• said controller predicts, based on a command sent from said controller to said unit side, a data amount of a response from the unit side for the command having been sent, stores data from said unit side sequentially, in a receive buffer, and does not store in the receive buffer, a portion of the data from the unit side, the portion exceeding the data amount having been predicted.

A communication data handling method in an image forming apparatus comprising a unit and a controller to control the unit, the image forming apparatus performing data sending and receiving between the unit and the controller, wherein,

• said controller predicts, based on a command sent from said controller to said unit side, a data amount of a response from the unit side for the command having been sent, measures the data amount of said response from said unit side, and performs communication error processing when the measured data amount of said response does not agree with the predicted data amount within a predetermined period of time.