UM0851 datasheet(105/245 Pages) STMICROELECTRONICS

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UM0851

Communication device drivers

Doc ID 16604 Rev 2

105/245

4.9

CAN driver

CAN is a message based protocol designed specifically for automotive applications, but now

also used in other areas such as industrial automation and medical equipment.

This section describes the driver for the SPEAr320 CAN controller.

4.9.1

Hardware overview

Note:

Available only on SPEAr320

SPEAr320 provides two independent CAN bus interfaces fully compliant to CAN 2.0

protocol specifications (both Part A and Part B) within its standard customization.

The main features provided by the CAN IP are listed below:

●

Bit rates up to 1 MBit/s

●

32 Message objects

●

Each Message object has its own identifier mask

●

Programmable FIFO mode (concatenation of message objects)

●

Maskable interrupt

●

Disabled automatic retransmission mode for time triggered CAN applications

●

Programmable loop-back mode for self-test operation

CAN IPs in SPEAr support the following test modes. The test mode is entered by setting bit

test in the CAN control register to one. In test mode, the bits Tx1, Tx0, LBack, Silent and

Basic in the test register are writable:

●

Silent mode

–

In this mode, the IP is able to receive valid data frames and valid remote frames,

but it sends only recessive bits on the CAN bus and it cannot start a transmission.

–

It can be used to analyze the traffic on a CAN bus without affecting it by the

transmission of dominant bits (acknowledge bits, error frames).

●

Loopback mode

–

In loop back mode, the CAN core treats its own transmitted messages as received

messages and stores them (if they pass acceptance filtering) into a receive buffer.

●

Loopback combined with silent mode

This mode can be used for a "hot self test", meaning the CAN IP can be tested without

affecting a running CAN system connected to the pins CAN_TX and CAN_RX.

●

Basic mode

In this mode the CAN IP runs without the Message RAM.

Note:

For further details please refer to SPEAr320 user manual

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