[AUTOSAR XIII NVM]

1. NvM（Nonvolatile Memory Manager）

NvM Can manage Flash、EEPROM These memories , Have achieved unified management of different hardware :

• Queue management mechanism
• Power on / off storage processing
• Support data verification
• Write protection of data
• Redundant storage of data

1.1 Queue management mechanism

When there is data you want to save Memory When , because Flash and EEPROM You need to erase before writing , Faster than RAM A lot slower , So there will be data queuing .

•	 The queuing mechanism can be manually configured as FIFO Or queue with priority 
•	 You can configure the depth of the queue 
•	 Support immediate data （immediate data, That is, the data required to be written immediately , such as crash data） Fast write , That is, there is no need to queue 

1.2 Power on / off storage processing

•	 When the power is on , To read NV The necessary data in 
•	 When the power is off , Write the necessary data NV Inside 

1.3 Support data verification

Mainly used CRC Check whether the data is wrong

•	 When the verification is wrong , Trigger use default data （ It can be used directly or CallBack）

1.4 Write protection of data

As we write Flash Unlock it first ; Another way is to set single write , Only one write is allowed

1.5 Redundant storage of data

The main thing is to increase the reliability of some key data

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2. Fee

Fee（Flash EEPROM Emulation） It's right Falsh Imitation EEP An abstract concrete implementation of .

Flash It is abstracted into one by one Flash Sector,Flash Sector And divided into one by one Flash Page.

• Flash Sector： Namely Flash Smallest erasable unit , It can also be configured to be larger

• Flash Page： Fee Only through Flash Page To visit Flash, That is to say Fee The smallest unit of ,Flash Sector contain Flash Page.

• Fee Would call Flash drive （FLS） To realize the real functions of erasing and writing hardware ; however Flash Due to life span , You can't always erase the same address Flash, therefore Fee It also automatically manages the address written , Try to write data evenly

• Fee Yes Flash When writing , It will be backed up first , Then erase . That means we need at least two Flash Sector. The process is ： The first thing to erase Sector All data is backed up to another Sector in , Then erase the Sector, The next one page One page Of write data , Until this Sector Write full

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3. Ea

Ea（EEPROM Abstraction） It's right EEPROM The abstraction of , It also calls EEPROM The driver （EEP） To achieve the final operation .

It will, too consider EEPROM To make an equal share of the stored data . but Ea And Flash The difference is ,EEPROM There is no need to erase piece by piece , It's more flexible , Sure Write data at a fixed point . So it can put a Block Write several Memroy Locations Inside .

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4. NVM Storage processing and Block

4.1 NVRAM Block

NVRAM Block Generally, it only contains 1 individual RAM Block、1 individual Administrative Block and 0/1 individual ROM Block. however NV Block It can contain more than one , It includes several NV Block, We will NVRAM Block There are three types ：Native（ normal ）、Redundant（ redundancy ） and Dataset（ Data sets ）.

• Native： That is, a RAM Block Save to the corresponding NV Block in
• Redundant： Will a RAM Block Save to two NV Block in , When one data fails, another can be used
• Dataset： Most support 255 individual NV Block, It's like an array , It can be used DataIndex To index the data

4.2 Fee Block

Fee Block Is in Fee Used in Block, It's called “Chunks” The way to do management .

One Chunk It can contain several Blocks, and Chunk They are connected in the form of a linked list ,Chunk Is one of the nodes

 If NVRAM Block Of Block Length If so 16, that Fee Block Of Block Size We should add CRC length （CRC16 Add 2,CRC32 Add 4）.
 So if it is CRC32, that Fee Block Of Block Size It should be for 20.

 Below Ea Block Is the same 

4.3 Ea Block