Data communication system

A data communication system for transmitting data signals between a first control unit and a second control unit, comprising:

• a clock signal line for transmitting a clock signal from said first control unit to said second control unit;
• a first data signal line for transmitting a first data signal from said first control unit to said second control unit in synchronism with said clock signal;
• a first trigger signal line for transmitting a first trigger signal from said first control unit to said second control unit for informing said second control unit of start of transmission of said first data signal;
• a second data signal line for transmitting a second data signal from said second control unit to said first control unit in synchronism with said clock signal;
• and
• a second trigger signal line for transmitting a second trigger signal from said second control unit to said first control unit for informing said first control unit of start of transmission of said second data signal,
• wherein said first data signal is transmitted from said first control unit to said second control unit when said first trigger signal is transmitted from said first control unit to said second control unit via said first trigger signal line, and
• wherein said second data signal is transmitted from said second control unit to said first control unit when said second trigger signal is transmitted from said second control unit to said first control unit via said second trigger signal line.