Enum Priority 

#[repr(u8)]
pub enum Priority {
    Exceptional = 0,
    Immediate = 1,
    Fast = 2,
    High = 3,
    Nominal = 4,
    Low = 5,
    Slow = 6,
    Optional = 7,
}

Transfer priority [1; 4.1.1.3]

The type has explicit numeric encoding to facilitate look-up table implementation. The encoding matches the CAN ID encoding [1; 4.2.1.1], thus the ordering is reversed: Optional > Exceptional

Variants

Exceptional = 0

The bus designer can ignore these messages when calculating bus load since they should only be sent when a total system failure has occurred. For example, a self-destruct message on a rocket would use this priority. Another analogy is an NMI on a microcontroller.

Immediate = 1

Immediate is a “high priority message” but with additional latency constraints. Since exceptional messages are not considered when designing a bus, the latency of immediate messages can be determined by considering only immediate messages.

Fast = 2

Fast and immediate are both “high priority messages” but with additional latency constraints. Since exceptional messages are not considered when designing a bus, the latency of fast messages can be determined by considering only immediate and fast messages.

High = 3

High priority messages are more important than nominal messages but have looser latency requirements than fast messages. This priority is used so that, in the presence of rogue nominal messages, important commands can be received. For example, one might envision a failure mode where a temperature sensor starts to load a vehicle bus with nominal messages. The vehicle remains operational (for a time) because the controller is exchanging fast and immediate messages with sensors and actuators. A system safety monitor is able to detect the distressed bus and command the vehicle to a safe state by sending high priority messages to the controller.

Nominal = 4

This is what all messages should use by default. Specifically, heartbeat messages should use this priority.

Low = 5

Low priority messages are expected to be sent on a bus under all conditions but cannot prevent the delivery of nominal messages. They are allowed to be delayed, but latency should be constrained by the bus designer.

Slow = 6

Slow messages are low priority messages that have no time sensitivity at all. The bus designer need only ensure that for all possible system states, these messages will eventually be sent.

Optional = 7

These messages might never be sent (theoretically) for some possible system states. The system shall tolerate never exchanging optional messages in every possible state. The bus designer can ignore these messages when calculating bus load. This should be the priority used for diagnostic or debug messages that are not required on an operational system.

Implementations

impl Priority

pub const MIN: Priority = Priority::Exceptional

pub const MAX: Priority = Priority::Optional

pub const fn try_from_u8(code: u8) -> Option<Priority>

pub const fn from_u8_truncating(code: u8) -> Priority

pub const fn into_u8(self) -> u8

pub const fn next(self) -> Option<Self>

pub const fn prev(self) -> Option<Self>

Trait Implementations

impl Clone for Priority

fn clone(&self) -> Priority

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Priority

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl From<Priority> for u8

fn from(value: Priority) -> Self

Converts to this type from the input type.

impl From<Priority> for usize

fn from(value: Priority) -> Self

Converts to this type from the input type.

impl Ord for Priority

fn cmp(&self, other: &Priority) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized,

Restrict a value to a certain interval.

impl PartialEq for Priority

fn eq(&self, other: &Priority) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl PartialOrd for Priority

fn partial_cmp(&self, other: &Priority) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &Rhs) -> bool

Tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

Tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

Tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

Tests greater than or equal to (for self and other) and is used by the >= operator.

impl TryFrom<u8> for Priority

type Error = InvalidValue

The type returned in the event of a conversion error.

fn try_from(value: u8) -> Result<Self, Self::Error>

Performs the conversion.

impl Copy for Priority

impl Eq for Priority

impl StructuralPartialEq for Priority