PIC18F258-ESLASHLSQTP datasheet(201/402 Pages) MICROCHIP

201 / 402 page

DS41159E-page 199

PIC18FXX8

19.0

CAN MODULE

19.1

Overview

The Controller Area Network (CAN) module is a serial

interface, useful for communicating with other peripher-

als or microcontroller devices. This interface/protocol

was designed to allow communications within noisy

environments.

The CAN module is a communication controller,

implementing 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 implemen-

tation 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:

• Complies with ISO CAN Conformance Test

• 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

• 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

• 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

19.1.1

OVERVIEW OF THE MODULE

The CAN bus module consists of a protocol engine and

message buffering and control. The CAN protocol

engine handles all functions for receiving and transmit-

ting 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 2 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

CAN module uses RB3/CANRX and RB2/CANTX/INT2

pins to interface with CAN bus. In order to configure

CANRX and CANTX as CAN interface:

• bit TRISB<3> must be set;

• bit TRISB<2> must be cleared.

19.1.2

TRANSMIT/RECEIVE BUFFERS

The PIC18FXX8 has three transmit and two receive

buffers, two acceptance masks (one for each receive

buffer) and a total of six acceptance filters. Figure 19-1

is a block diagram of these buffers and their connection

to the protocol engine.

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