Bxcan General Description; Can 2.0B Active Core; Control, Status And Configuration Registers; Tx Mailboxes - STMicroelectronics RM0365 Reference Manual

Controller area network (bxCAN)
31.3

bxCAN general description

In today's CAN applications, the number of nodes in a network is increasing and often
several networks are linked together via gateways. Typically the number of messages in the
system (and thus to be handled by each node) has significantly increased. In addition to the
application messages, Network Management and Diagnostic messages have been
introduced.
•
An enhanced filtering mechanism is required to handle each type of message.
Furthermore, application tasks require more CPU time, therefore real-time constraints
caused by message reception have to be reduced.
•
A receive FIFO scheme allows the CPU to be dedicated to application tasks for a long
time period without losing messages.
The standard HLP (Higher Layer Protocol) based on standard CAN drivers requires an
efficient interface to the CAN controller.
31.3.1

CAN 2.0B active core

The bxCAN module handles the transmission and the reception of CAN messages fully
autonomously. Standard identifiers (11-bit) and extended identifiers (29-bit) are fully
supported by hardware.
31.3.2

Control, status and configuration registers

The application uses these registers to:
•
Configure CAN parameters, e.g. baud rate
•
Request transmissions
•
Handle receptions
•
Manage interrupts
•
Get diagnostic information
31.3.3

Tx mailboxes

Three transmit mailboxes are provided to the software for setting up messages. The
transmission Scheduler decides which mailbox has to be transmitted first.
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Figure 378. CAN network topology

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RM0365