PIC18F4680ISPQTP datasheet(275/482 Pages) MICROCHIP

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Preliminary

DS39625C-page 273

PIC18F2585/2680/4585/4680

23.0

ECAN™ TECHNOLOGY

PIC18F2585/2680/4585/4680

devices

contain

Enhanced Controller Area Network (ECAN) module.

The ECAN module is fully backward compatible with

the CAN module available in PIC18CXX8 and

PIC18FXX8 devices.

The Controller Area Network (CAN) module is a serial

interface which is useful for communicating with other

peripherals or microcontroller devices. This interface,

or protocol, was designed to allow communications

within noisy environments.

The ECAN module is a communication controller, imple-

menting the CAN 2.0A or 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; however, the CAN specification is not

covered within this data sheet. 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

• DeviceNetTM data bytes filter support

• Standard and extended data frames

• 0-8 bytes data length

• Programmable bit rate up to 1 Mbit/sec

• Fully backward compatible with PIC18XXX8 CAN

module

• Three modes of operation:

- Mode 0 – Legacy mode

- Mode 1 – Enhanced Legacy mode with

DeviceNet support

- Mode 2 – FIFO mode with DeviceNet support

• Support for remote frames with automated handling

• Double-buffered receiver with two prioritized

received message storage buffers

• Six buffers programmable as RX and TX

message buffers

• 16 full (standard/extended identifier) acceptance

filters that can be linked to one of four masks

• Two full acceptance filter masks that can be

assigned to any filter

• One full acceptance filter that can be used as either

an acceptance filter or acceptance filter mask

• Three dedicated transmit buffers with application

specified prioritization and abort capability

• 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 timer module for

time-stamping and network synchronization

• Low-power Sleep mode

23.1

Module Overview

The CAN bus module consists of a protocol engine and

message buffering and control. The CAN protocol

engine automatically 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 two receive registers.

The CAN module supports the following frame types:

• Standard Data Frame

• Extended Data Frame

• Remote Frame

• Error Frame

• Overload Frame Reception

• Interframe Space Generation/Detection

The CAN module uses the RB2/CANTX and RB3/

CANRX pins to interface with the CAN bus. In normal

mode, the CAN module automatically overrides

TRISB<2>. The user must ensure that TRISB<3> is

set.

23.1.1

MODULE FUNCTIONALITY

The CAN bus module consists of a protocol engine,

message buffering and control (see Figure 23-1). The

protocol engine can best be understood by defining the

types of data frames to be transmitted and received by

the module.

The following sequence illustrates the necessary initial-

ization steps before the ECAN module can be used to

transmit or receive a message. Steps can be added or

removed depending on the requirements of the

application.

Ensure that the ECAN module is in Configuration

mode.

Select ECAN Operational mode.

Set up the baud rate registers.

Set up the filter and mask registers.

Set the ECAN module to normal mode or any

other mode required by the application logic.

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