PIC24HJ128GP310 datasheet(173/286 Pages) MICROCHIP

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DS70175F-page 171

PIC24HJXXXGPX06/X08/X10

18.0 ENHANCED CAN MODULE

18.1

Overview

The Enhanced Controller Area Network (ECAN) mod-

ule is a serial interface, useful for communicating with

other CAN modules or microcontroller devices. This

interface/protocol was designed to allow communica-

tions

within

noisy

environments.

The

PIC24HJXXXGPX06/X08/X10 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.

18.2

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

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.

• 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

illegal condition. Second, due to internal condi-

tions, the node is not yet able to start reception of

the next message. A node may generate a maxi-

mum 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:

This data sheet summarizes the features

of this group of PIC24HJXXXGPX06/X08/

X10 devices. It is not intended to be a

comprehensive reference source. To com-

plement the information in this data sheet,

refer to the “PIC24H Family Reference

Manual”. Refer to the Microchip web site

(www.microchip.com)

for

the

latest

PIC24H

Family

Reference

Manual

sections.

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