uds+0x34+0x36

### UDS协议中0x34和服务0x38的区别及用法 #### 0x34 请求下载 (Request Download) 此服务用于初始化ECU接收新的应用软件或其他数据的过程。客户端通过发送`requestDownload`命令告知服务器即将进行文件或数据块的传输，并提供有关待传数据的信息。 - **参数说明** - `compressionMethod`: 高四位表示压缩方式，默认为无压缩(即0)[^2]。 - `encryptionMethod`: 低四位代表加密算法的选择，同样默认情况下也是未启用状态(即0)。 当接收到有效的`requestDownload`请求后，服务器会返回一个响应消息给客户端，其中包含了允许的最大数据长度以及可能的状态信息等细节[^1]。 ```python # Python伪代码展示如何构建0x34请求报文 def build_request_download(compression_method=0, encryption_method=0): # 构建0x34服务请求帧 service_id = 0x34 data_format_identifier = (compression_method << 4) | encryption_method request_frame = [ service_id, data_format_identifier, # ...其他必要字段... ] return bytes(request_frame) ``` #### 0x38 上传控制 (Transfer Control) 相比之下，`transferControl`(0x38)主要用于管理已建立连接上的数据流方向切换或是终止当前正在进行中的传输操作。它能够实现暂停、恢复乃至完全停止由之前发起的服务所触发的数据交换活动。 - **功能描述** - 控制正在执行的数据传输过程； - 支持多种动作选项，比如开始/继续(`START_OR_CONTINUE`)、停止并保持位置(`STOP_AND_KEEP_POSITION`)、取消整个事务(`CANCEL`)等； - 对于某些应用场景而言，还可以用来改变传输模式（例如从编程模式转换回正常运行模式）； ```python # Python伪代码展示如何构建0x38请求报文 def build_transfer_control(action_type): """ :param action_type: 动作类型常量之一， 如'START_OR_CONTINUE', 'STOP_AND_KEEP_POSITION' 或者'CANCEL' """ service_id = 0x38 actions_map = { "START_OR_CONTINUE": 0x01, "STOP_AND_KEEP_POSITION": 0x02, "CANCEL": 0x03 } control_option_record = actions_map[action_type] request_frame = [ service_id, control_option_record ] return bytes(request_frame) ``` 综上所述，在统一诊断服务(UDS)标准里，虽然两者都涉及到数据传送的操作，但是它们各自扮演着不同的角色：前者侧重于准备阶段的工作，后者则是针对已有链接实施更精细的行为调控措施。

### UDS ISO 14229-1 Diagnostic Service 0x34 Explanation and Usage The UDS (Unified Diagnostic Services) service with identifier `0x34` is defined as the Request Download Transfer Control function according to the standard ISO 14229-1[^1]. This service allows a client, typically an external diagnostic tool or another ECU, to request that data be downloaded into a specific memory area of the target ECU. #### Purpose This service facilitates transferring application software or configuration parameters from one device to another within vehicles. It plays a crucial role during vehicle maintenance when firmware updates are necessary. #### Parameters Involved When using this command, several sub-function codes can specify different actions related to managing download transfers: - **Request to start routine**: Initiates preparation for receiving new data. - **Transfer Data Block**: Sends actual binary content intended for storage on the destination system. - **Request transfer exit**: Signals completion once all required information has been successfully transmitted. Each operation requires appropriate parameter sets including addresses where bytes should reside after being written along with lengths indicating how much space will hold incoming values. For example, initiating a session might look like sending `0x34 0x01`, which requests starting conditions before any file transmission begins. ```python def send_request_download_command(sub_function_code): """ Constructs a UDS message for requesting download control Args: sub_function_code (int): Subfunction code specifying action type Returns: list[int]: Message frame containing service ID followed by arguments """ return [0x34, sub_function_code] # Example usage start_routine_message = send_request_download_command(0x01) print(start_routine_message) ```