ST92F124 datasheet(325/429 Pages) STMICROELECTRONICS

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CONTROLLER AREA NETWORK (bxCAN)

10.10 CONTROLLER AREA NETWORK (bxCAN)

10.10.1 Introduction

This peripheral Basic Extended CAN, named bx-

CAN, interfaces the CAN network. It supports the

CAN protocol version 2.0A and B. It has been de-

signed to manage a high number of incoming mes-

sages efficiently with a minimum CPU load. It also

meets the priority requirements for transmit mes-

sages.

For safety-critical applications, the CAN controller

provides all hardware functions for supporting the

CAN Time Triggered Communication option.

10.10.2 Main Features

■ Supports CAN protocol version 2.0 A, B Active

■ Bit rates up to 1Mbit/s

■ Supports the Time Triggered Communication

option

Transmission

■ Three transmit mailboxes

■ Configurable transmit priority

■ Time Stamp on SOF transmission

Reception

■ Two receive FIFOs with three stages

■ Eight scalable filter banks

■ Identifier list feature

■ Configurable FIFO overrun

■ Time Stamp on SOF reception

Time Triggered Communication Option

■ Disable automatic retransmission mode

■ 16-bit free running timer

■ Configurable timer resolution

■ Time Stamp sent in last two data bytes

Management

■ Maskable interrupts

■ Software-efficient mailbox mapping at a unique

address space

10.10.3 General Description

In today’s CAN applications, the number of nodes

in a network is increasing and often several net-

works are linked together via gateways. Typically

the number of messages in the system (and thus

to be handled by each node) has significantly in-

creased. 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 pe-

riod without losing messages.

The standard HLP (Higher Layer Protocol) based

on standard CAN drivers requires an efficient in-

terface to the CAN controller.

– All mailboxes and registers are organized in 16-

byte pages mapped at the same address and se-

lected via a page select register.

Figure 142. CAN Network Topology

CAN

High

Low

CAN

Transceiver

CAN

Controller

ST9 MCU

CAN Bus

Application

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