###### tags: `報告`
# ara::nm 2 : NM Messages

Documents:
[SWS_NetworkManagement](https://www.autosar.org/fileadmin/user_upload/standards/adaptive/21-11/AUTOSAR_SWS_NetworkManagement.pdf)
[PRS_NetworkManagementProtocol](https://www.autosar.org/fileadmin/user_upload/standards/foundation/21-11/AUTOSAR_PRS_NetworkManagementProtocol.pdf)
[ara::nm(last time)](https://hackmd.io/@NCKU-autosar/ByRW93zfj)

## NM Message Format


### What does NM Message do?
When different nodes communicate with each other(either in `Repeat Message State` or `Normal Operation State`), they send a formatted data named `NM Message`. After receiving the message in Network Mode [(that we mentioned last time)](https://hackmd.io/@NCKU-autosar/ByRW93zfj#Network-Mode), the NM Instance will work according to the message.

### Control Bit Vector(CBV)
Control Bit Vector can be configured to be put in `Byte 0, 1 or Off (aka Optional)`. There are 6 bits that is used in this vector(bits 2, 7 are preserved).

#### KNOWN LIMITATIONS
According to specification of NM(SWS_NetworkManagement, Ch4.1), the adaptive NM doesn't support following:
* Doesn't support `Node Detection`, it only handles incoming requests.
* Cannot be configured as `NM Coordinator`, so it doesn't support `Coordinated Shutdown`.
* `Passive Startup/Wakeup`

Because of above reasons, ony two bits will be using when transmitting NM Messages:

#### Bit 1: PN Shutdown Request Bit (PNSR)
Will be visited in `Partial Network` Chapter.

#### Bit 6: Partial Network Information Bit (PNI)

When this is set to 1, NM Message contains Partial Network request information.

### Source Node Identifier(SNI)

Each node should have a unique ID(`nmNodeID`) when transmitting NM Message. This ID should be placed in `Byte 1, 0 or Off (aka Optional)`.

### User Data

User Data is the data other than CBV and SNI. The length is defined by `nmUserDataLength`.