L99LDLH32 datasheet(44/142 Pages) STMICROELECTRONICS

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Communication interface

L99LDLH32

44/142

DS12879 Rev 6

Also a wake-up over the network is implemented.

6.3.1

CAN FD Light compatible frame format

The CAN FD base format is used for the CAN FD Light compatible protocol without

extended ID implemented as shown in Figure 17.

Figure 17. CAN FD Base Frame Format (FBFF)

The bits in the control field are fixed: FD frame (FDF) is always recessive. Not supported are

extended ID (EID, IDE bit always dominant), bit rate switch (BRS, always dominant) and

error state indication (ESI, always dominant).

The data field can be up to 64 bytes long, the number of bytes is encoded in the data length

code (DLC) field. Depending on the number of data bytes either CRC17 or CRC21 is

calculated. Only one CRC delimiter bit is sent and accepted since the data bit rate is the

same as the arbitration bit rate.

The arbitration and data bit rate are both 1 Mb/s. The bit rate is not switched.

6.3.2

Wake-Up

The Responders support a power down mode out of which they can be woken up by the

wake-up frame shown in Table 10.

6.3.3

Error frames

No error frames are sent by the Responders. Error frames may be sent by the Commander,

but are ignored by the Responders.

6.3.4

Collisions

Since the communication is always controlled and initiated by the Commander, the bus

participants do not arbitrate. Collisions lead to data frame errors.

6.3.5

Error handling

Network participant disconnect

Since all participants share the same bus various mechanisms allow the detection of a

disconnected device.

After each sent frame at least one acknowledge is expected from a receiver. If this

acknowledge is not received it can be assumed that the sender is not connected to the

network.

Broadcast frames can be transmitted within a given interval. Responders not receiving a

broadcast frame after a defined time may have lost their connection to the Commander.

IFS

SOF

Std ID (11 Bit)

FDF

IDE

res

DLC<3:0>

Data Field (max. 64 Bytes)

CRC <16:0> / <20:0>

ACK

Slot

ACK

CRC

Delimiter Delimiter

EOF <6:0>

RRS

BRS

ESI

IFS

FD Base Frame

Format Light

Arbitration

Field

Data Field

Control Field

CRC Field

ACK Field

EOF

Stuff Bit Count

<2:0>

Parity

FBFF Light

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