DSPIC30F4012 datasheet(129/238 Pages) MICROCHIP

129 / 238 page

DS70135G-page 129

dsPIC30F4011/4012

19.0

CAN MODULE

19.1

Overview

The Controller Area Network (CAN) module is a serial

interface, useful for communicating with other CAN

modules or digital signal controller devices. This inter-

face/protocol was designed to allow communications

within noisy environments. The dsPIC30F4011/4012

devices have 1 CAN module.

The CAN module is a communication controller imple-

menting the CAN 2.0 A/B protocol, as defined in the

BOSCH specification. The module will support CAN 1.2,

CAN 2.0A, CAN2.0B Passive and CAN 2.0B Active

versions of the protocol. The module implementation is

a full CAN system. The CAN specification is not covered

within this data sheet. The reader may refer to the

BOSCH CAN specification for further details.

The module features are as follows:

• Implementation of the CAN protocol CAN 1.2,

CAN 2.0A and CAN 2.0B

• Standard and extended data frames

• 0-8 bytes data length

• Programmable bit rate up to 1 Mbit/sec

• Support for remote frames

• Double-buffered receiver with two prioritized

received message storage buffers (each buffer

may contain up to 8 bytes of data)

• 6 full (standard/extended identifier), acceptance

filters, 2 associated with the high priority receive

buffer and 4 associated with the low priority

receive buffer

• 2 full, acceptance filter masks, one each associated

with the high and low priority receive buffers

• Three transmit buffers with application specified

prioritization and abort capability (each buffer may

contain up to 8 bytes of data)

• Programmable wake-up functionality with

integrated low-pass filter

• Programmable Loopback mode supports self-test

operation

• Signaling via interrupt capabilities for all CAN

receiver and transmitter error states

• Programmable clock source

• Programmable link to input capture module (IC2,

for both CAN1 and CAN2) for time-stamping and

network synchronization

• Low-power Sleep and Idle mode

The CAN bus module consists of a protocol engine and

message buffering/control. The CAN protocol engine

handles all functions for receiving and transmitting

messages on the CAN bus. Messages are transmitted

by first loading the appropriate data registers. Status

and errors can be checked by reading the appropriate

registers. Any message detected on the CAN bus is

checked for errors and then matched against filters to

see if it should be received and stored in one of the

receive registers.

19.2

Frame Types

The CAN module transmits various types of frames

which include data messages or remote transmission

requests, initiated by the user, as other frames that are

automatically generated for control purposes. The

following frame types are supported:

19.2.1

STANDARD DATA FRAME

A standard data frame is generated by a node when the

node wishes to transmit data. It includes an 11-bit

Standard Identifier (SID) but not an 18-bit Extended

Identifier (EID).

19.2.2

EXTENDED DATA FRAME

An extended data frame is similar to a standard data

frame but includes an extended identifier as well.

19.2.3

REMOTE FRAME

It is possible for a destination node to request the data

from the source. For this purpose, the destination node

sends a remote frame with an identifier that matches

the

identifier

of the required

data

frame. The

appropriate data source node will then send a data

frame as a response to this remote request.

19.2.4

ERROR FRAME

An error frame is generated by any node that detects a

bus error. An error frame consists of 2 fields: an error

flag field and an error delimiter field.

19.2.5

OVERLOAD FRAME

An overload frame can be generated by a node as a

result of 2 conditions. First, the node detects a domi-

nant bit during interframe space which is an illegal

condition. Second, due to internal conditions, the node

is not yet able to start reception of the next message. A

node may generate a maximum of 2 sequential

overload frames to delay the start of the next message.

19.2.6

INTERFRAME SPACE

Interframe space separates a proceeding frame (of

whatever type) from a following data or remote frame.

Note:

This data sheet summarizes features of

this group of dsPIC30F devices and is not

intended to be a complete reference

source. For more information on the CPU,

peripherals,

descriptions

and

general device functionality, refer to the

dsPIC30F

Family

Reference

Manual

(DS70046). For more information on the

device instruction set and programming,

refer to the “16-bit MCU and DSC

Reference Manual” (DS70157).

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