Information Bus: Description and Operation

GENERAL DESCRIPTION

CAN, an abbreviation for Controller Area Network, is an ISO-certified international standard for a serial multiplex communication protocol*.
NOTE:
*: The regulations have been decided in detail, from software issues such as the necessary transmission rate for communication, the system, data format, and communication timing control method to hardware issues such as the harness type and length and the resistance values.

A communication circuit employing the CAN protocol connects each ECU, and sensor data can be shared among, which enables more reduction in wiring.

CAN offers the following advantages.

- Transmission rates are much faster than those in conventional communication (up to 1 Mbps), allowing much more data to be sent.
- It is exceptionally immune to noise, and the data obtained from each error detection device is more reliable.
- Each ECU connected via the CAN communicates independently, so if the ECU enters damaged mode, communications can be continued in some cases.











STRUCTURE





- The CAN bus line consists of two lines, CAN_L and CAN_H (CAN Low and CAN High, respectively), as well as two terminal resistors. (A twisted-pair cable, highly resistant to noise, is used for the communications line.)
- The CAN bus line connecting the two terminal resistors is the main bus line, and the CAN bus line connecting each ECU is the sub-bus line.
- The terminal resistors are installed in the engine-control module (ECM) [M/T] or powertrain control module (PCM) [A/T] and combination meter to stabilize communication signals. (Each terminal resistance is set at approximately 120 ohms.)
- The TCL/ASC-ECU and convertible top control module[ ECLIPSE SPYDER] are branched internally, with one line connected to the TCL/ASC-ECU and convertible top control module[ ECLIPSE SPYDER] and the other connected to the powertrain control module (PCM).
- To the CAN bus line, equipments with control module and data link connector are connected as follows for each network.
- Engine control module (ECM) [M/T] or powertrain control module (PCM) [A/T]
- TCL/ASC-ECU
- Convertible top control module[ ECLIPSE SPYDER]
- ETACS-ECU
- TPMS receiver
- A/C-ECU
- SRS-ECU
- Combination meter
- Steering wheel sensor