日本三菱汽车格蓝迪CAN-BUS培训教材.pptVIP

How the lead time of the information could cause wrong messages How the synchronisation is made by shorten the bit time. Bus systems in MMC vehicles: K-Line , SWS, M-BUS and the structure and application in the car. K-Line is the Diagnosis lineand connects the test equipment (MUT II) with the ECU′s.The only sense of this bus is testing. SWS is used for body electronics such as electric windows etc. It is used for the comunication between the different ECU′s. M-Bus is used for audio and navigation equipment. Not in the scheme and so far only used for M-ASTC is CAN Bus M-Bus uses 3 different lines: one is for synchronisation, one is to detect if another unit is sending and the third is the data line. Different then in the bit time adjusting, here the time signal is send to the receiver as well and makes thereby sure that the complete message is receipt.(Time delay of clock signal is same as for data. SWS uses cyclic communication. One communication period is 40 ms.In that time all ecu′s get the sending permission.SWS uses the token control to forward the sending permission to the next unit. Twisted wire is used to reduce sensitivity against noise. The signal between high and ground is opposite to the signal low to ground, so that noise only can reduce one of them, the other is even increased.= no wrong info due to noise. Can is a so called multi master bus, whic means every station can become master and send a message.Communication is event driven.If an Ecu wants to send a message it transfersit to the can controller,which will send it if bus is free or he has highest priorty. Twisted wire is used, but if forseen CAN can work also with a single wire.Speed of data transmission can reach 1 Mbit but in reality 500kbit rate is used .(Also by MMC) In order to produce the digital signal the tension of both the high and low side is changed by the can controller. The Can layout we use is a three ?wire“ layout. The bit 1 is represented by 2.5 Volt on both high and low =d