AUTOSAR COM学习（一）

AUTOSAR的COM模块从本质上来讲就是处理信号的接收和发送事宜，简化后就像下图这个样子，一进一出，有来有回：

• 信号滤波

COM支持的信号级滤波算法见下表：

Name	Algorithm	Description
ALWAYS	True	No filtering is  performed so that the message always passes.
NEVER	False	The filter  removes all messages.
MASKED_NEW_EQUALS_X	(new_value&mask)  == x	Pass messages  whose masked value is equal to a specific value.
MASKED_NEW_DIFFERS_X	(new_value&mask)  != x	Pass messages  whose masked value is not equal to a specific value.
MASKED_NEW_DIFFERS_MASKED_OLD	(new_value&mask)  != (old_value&mask)	Pass messages  where the masked value has changed.
NEW_IS_WITHIN	min <= new_value  <= max	Pass a message if  its value is within a predefined boundary.
NEW_IS_OUTSIDE	(min >  new_value) || (new_value > max)	Pass a message if  its value is outside a predefined boundary.
ONE_EVERY_N	Occurrence%period  == offset	Pass a message  once every N message occurrences. Start:  occurrence=0. Each time the  message is received or transmitted, occurrence is incremented by 1 after  filtering. Length of  occurrence is 8 bit(minimum).

表中前7种算法结合描述比较容易理解，最后一种ONE_EVERY_N是指在period次filter中只有第offset次才能通过，打个比方有8个跑马灯编号0-7，循环点亮，指定编号2的灯亮时滤波通过。

• 信号组

COM模块提供将多个信号打包成组看作一个整体来处理的功能：

和普通信号处理相比，信号组增加了两个接口Com_SendSignalGroup