1. 制动信息一致性比较Accordance comparison of braking information
对于制动命令的输出，两个CPU应采用跟随的方式，即在所有输入信息一致的情况下，没有输出制动命令的一系应当跟随输出制动命令的一系输出制动命令，硬件应当能够容忍两个CPU在制动命令输出时间上的间隔；反之，只有当两个CPU均取消制动命令时，整个VC系统才会取消制动。
With respect to the braking order output, the two CUPs should work in the manner of follow, that is, under the consistent input information circumstances, one system without outputting braking order should follow the action that another system outputs braking order, hardware unit should stand the interval of braking order output from two CUPs; contrarily, the whole VC system can cancel braking order only when both CUPs cancel braking order.
2. 与外设通信数据一致性比较Accordance comparison of data communicating with peripheral device
LKJ、BTM以及DMI的通讯接口为一个RS422接口，如果与VC中两个CPU相对应，需要对RS422通讯进行2合1。
Communication interface of LKJ, BTM and DMI is RS422, if it needs to be uniformed with two CPUs in VC system, then two into one action should be done for RS422 communication interface.
为实现通信的合并，采用总线仲裁的方式，即每个CPU均向外发送数据，由硬件将数据进行合并处理后发送给外设。为满足总线仲裁的要求，需要满足以下的两个条件：
Bus arbitration is used to realize communication combination, that is, both CPUs send out data, then data to be combined and processed by hardware and send to peripheral device. To satisfy the requirement of bus arbitration, following two specifications to be satisfied firstly:
1． 两个CPU向外设发送的数据应当是一致的；
1.  The data send to peripheral device by two CPUs should be accordant;
2． 两个CPU向外设发送数据的间隔应当小于2ms。
2.  The interval that two CPUs send data to peripheral device should be less than 2ms.
为满足第一个条件，两个CPU在向外设发送数据之前应当进行一致性的比较，对于模拟量数据，在满足误差范围的要求后，统一采用偏向安全方的数据；对于状态量数据，则必需是一致的，否则本次不进行发送。
To satisfy the first requirement, accordant comparison should be done by two CPUs before sending to peripheral device .For the analogue data, data leaned to security will be adopted after satisfying requirement of error range ;for status data, which needs to be accordant, otherwise ,it will not be output at this time.

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为满足第二个条件，两个CPU之中的软件应当满足弱任务同步。
To satisfy the second requirement, softwares belong to two CPUs should be satisfied task synchronization.
在满足以上两个条件下，两个CPU才可以与总线仲裁模块通信。根据两个CPU与总线仲裁模块的通信方式的不同可分为RS422通信方式和外部RAM访问方式。
 Two CPUs can communicate with bus arbitration module till satisfy above two requirements. Communication between two CPUs and bus arbitration module can be divided into RS422 type and exterior RAM access according to different communication.
接口——interface
总线仲裁——bus arbitration
通信数据包——communication data package
外设——peripheral device
数据比较——data compare
等待2ms——waiting for 2ms
数据一致否？——whether data is accordant or not
是否超过等待容限——whether exceed waiting limit or not
发送数据——send data
故障——failure
是——Yes
否——No
RS422通信方式：CPU在准备好数据发送后，向总线仲裁模块发送通信请求，总线仲裁模块同意进行通信后，两路CPU通过RS422，以固定的波特率将数据发送给总线仲裁模块，总线仲裁模块在规定的时间内接收完两路的数据后，对两路数据进行比较。
RS422 communication: CPU will send communication request to bus arbitration module after data is prepared, two CPUs will send data to bus arbitration module in constant Baud rate through RS422 when bus arbitration module permits to communicate, then bus arbitration module will compare two-channel data within setting time after receiving data .
数据比较结果若一致，总线仲裁模块向外设发送数据，并通知CPU数据通信成功；若比较结果不一致且超出等待时间，则协系统进入总线比较故障状态。
RS422 communication: CPU will send communication request to bus arbitration module after data is prepared, two CPUs will send data to bus arbitration module in constant Baud rate through RS422 when bus arbitration module permits to communicate, then bus arbitration module will compare two-channel data within setting time after receiving data .
接口——interface
总线仲裁——bus arbitration
通信数据包——communication data package
外设——peripheral device
数据比较——data compare
等待2ms——waiting for 2ms
数据一致否？——whether data is accordant or not
是否超过等待容限——whether exceed waiting limit or not
发送数据——send data
故障——failure
外部RAM访问方式：总线仲裁模块通过开辟两块RAM空间来接收CPU通信数据。CPU在准备好数据发送后，向总线仲裁模块发送通信请求，总线仲裁模块同意进行通信后，CPU将数据写入对应的外部RAM中，总线仲裁模块接收到两路数据后，进行数据比较，比较方法与上一方式相同。比较后的处理方法与上一方式相同。
Exterior RAM access: Bus arbitration module is to receive CPU communication data by establishing two RAM spaces. CPU will send communication request to bus arbitration module after data is prepared, CPU will write data into corresponding exterior RAM when bus arbitration module permits to communicate, bus arbitration module will compare data after receiving two-channel data ,comparison method is the same to the above method as well as the process method.