CAN Communication Signal
CAN communication system is a serial communication system to transmit a multiple number of data (values from sensors, control data and control signals) as ON-OFF digital signals through the communication line. This system uses two communication lines (CAN High and CAN Low) for the communication circuit so as to maintain high reliability even when used for the high-speed serial communication.
The serial communication takes place as shown below with 2.5 V as the reference level for both CAN High signal (1) and CAN Low signal (2). The range of CAN High signal is from 2.5 V to about 3.5 V and that of CAN Low signal is from 2.5 V to about 1.5 V. When both of them are 2.5 V, the signal is judged as OFF and when CAN High signal is 3.5 V and CAN Low signal is 1.5 V (that is, when the High to Low voltage difference is more than about 2 V) the signal then is judged as ON. For this reason, it is a feature of CAN communication signal that the signal waveform is symmetrical between CAN High and CAN Low signals with respect to the 2.5 V level. CAN communication fails when such signal form collapses.