70592C datasheet(181/314 Pages) MICROCHIP

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DS70592C-page 181

PIC24HJXXXGPX06A/X08A/X10A

19.0 ENHANCED CAN (ECAN™)

MODULE

19.1

Overview

The Enhanced Controller Area Network (ECAN™)

module is a serial interface, useful for communicating

with other CAN modules or microcontroller devices.

This interface/protocol was designed to allow commu-

nications

within

noisy

environments.

The

PIC24HJXXXGPX06A/X08A/X10A devices contain up

to two ECAN modules.

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, CAN 2.0B 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

• Automatic response to remote transmission

requests

• Up to 8 transmit buffers with application specified

prioritization and abort capability (each buffer may

contain up to 8 bytes of data)

• Up to 32 receive buffers (each buffer may contain

up to 8 bytes of data)

• Up to 16 full (standard/extended identifier)

acceptance filters

• 3 full acceptance filter masks

• DeviceNet™ addressing support

• 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, remote transmission

requests and as other frames that are automatically

generated for control purposes. The following frame

types are supported:

• 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).

• Extended Data Frame:

An extended data frame is similar to a standard data

frame but includes an extended identifier as well.

• 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 iden-

tifier 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.

• Error Frame:

An error frame is generated by any node that detects

a bus error. An error frame consists of two fields: an

error flag field and an error delimiter field.

• Overload Frame:

An overload frame can be generated by a node as a

result of two conditions. First, the node detects a

dominant bit during interframe space which is an ille-

gal 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.

• Interframe Space:

Interframe space separates a proceeding frame (of

whatever type) from a following data or remote

frame.

Note 1: This data sheet summarizes the features

of the PIC24HJXXXGPX06A/X08A/X10A

family of devices. However, it is not

intended to be a comprehensive refer-

ence source. To complement the infor-

mation in this data sheet, refer to the

“dsPIC33F/PIC24H Family Reference

Manual”, Section 21. “Enhanced Con-

troller

Area

Network

(ECAN™)”

(DS70226), which is available from the

Microchip website (www.microchip.com).

2: Some registers and associated bits

described in this section may not be

available on all devices. Refer to

Section 4.0 “Memory Organization” in

this data sheet for device-specific register

and bit information.

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