OSEK通信规范：汽车电子统一通信环境
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OSEK通信（OSEK COM）是汽车控制单元应用软件的一种统一通信环境。它通过定义内部通信（在电子控制单元内的通信）和外部通信（网络化车辆节点间的通信）的通用软件通信接口和行为，增强了应用软件模块的可移植性。这种规范独立于使用的通信协议，旨在在一个ECU（电子控制单元）内描述其行为。
OSEK COM的设计考虑了与符合OSEK OS规范的操作系统一起使用的情况。对于如何在非OSEK操作系统上运行OSEK COM的信息，可以在附录A中找到。该技术标准旨在提供一种标准化的方法，以便汽车电子系统的不同组件能够有效地交换数据，无论这些组件是同一控制单元内部还是跨多个控制单元。
文档《OpenSystems and the Corresponding Interfaces for Automotive Electronics OSEK/VDX COM 3.0.3》介绍了通信的版本3.0.3，日期为2004年7月20日。这是一份官方发布的文档，替代了之前的所有版本，并且OSEK组织保留未经通知随时修改的权利。
文档结构包括介绍、交互层等部分。介绍部分详细阐述了需求、通信概念和文档结构。交互层是通信的核心，它包括消息接收和消息传输两个主要方面。
消息接收部分涵盖了接收概述、接收过滤、将消息数据复制到消息对象数据区以及将数据复制到应用程序消息的过程。同时，区分了未队列和已队列的消息类型。
消息传输部分则详细描述了发送消息的过程，这部分可能涉及设置优先级、调度和确保消息正确到达目标节点的机制。由于内容被截断，完整的传输过程可能包括消息排队、错误处理和确认机制等细节。
OSEK COM是汽车电子领域的一个关键标准，它提供了一套标准化的通信接口和流程，促进了汽车控制单元之间的互操作性和软件复用。理解和实施OSEK COM规范对于开发适应现代汽车网络需求的嵌入式软件至关重要。
OSEK/VDX
OSEK Communication
Specification 3.0.3
OSEK/VDX COM 3.0.3 by OSEK - 12 -
2.2 Message reception
This section states the services and the functionality requirements of the message reception
entity of the IL.
2.2.1 Message reception overview
The first few steps described in this section are applicable for external communication only.
Reception of a message starts with an indication of the delivery of its containing PDU from
the underlying layer. If this indication does not yield an error, the reception was successful. In
this case, an I-PDU Callout is called (if configured) and this PDU is copied into the I-PDU.
In the case of unsuccessful PDU reception error indication takes place and no data is
delivered to the IL. Error indication can lead to Message Reception Error notification
(Notification Class 3, described in section 2.6.1).
After copying the data into the I-PDU further processing is performed separately for each
contained message. If the I-PDU contains zero-length messages, these are processed last.
The Reception Deadline Monitoring takes place as described in section 2.5.1. Deadline
Monitoring can invoke Message Reception Error notification (Notification Class 3, described
in section 2.6.1) when the message reception deadline is missed because the I-PDU that
contains the message is not received in time.
Then, the message data is unpacked from the I-PDU and, if configured, a Network-order
Message Callout is called for the message. Message byte order conversion is performed to
convert from network representation to the representation on the local CPU and, if configured,
a CPU-order Message Callout is called for the message.
The following steps are applicable for both internal and external communication.
The filtering is applied to the message content. If the message is not filtered out, then the
message data is copied into the receiver message object.
After filtering, Message Reception notification (Notification Class 1, described in section
2.6.1) is invoked as appropriate. Notification is performed per message object.
Message data are copied from message object to application messages when the application
calls the ReceiveMessage or ReceiveDynamicMessage API services.
2.2.2 Reception filtering
Filtering provides a means to discard the received message when certain conditions, set by
message filter, are not met for the message value. The message filter is a configurable
function that filters messages out according to specific algorithms. For each message a
different filtering condition can be defined through a dedicated algorithm.
Filtering is only used for messages that can be interpreted as C language unsigned integer
types (characters, unsigned integers and enumerations).
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