PIC18F25K80 MICROCHIP [Microchip Technology], PIC18F25K80 Datasheet - Page 395

• Manufacturer Part Number: PIC18F25K80
• Manufacturer: MICROCHIP [Microchip Technology]

27.0
PIC18F66K80 family devices contain an Enhanced
Controller Area Network (ECAN) module. The ECAN
module is fully backward compatible with the CAN
module available in PIC18CXX8 and PIC18FXX8
devices and the ECAN module in PIC18Fxx80 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,
• DeviceNet
• Standard and extended data frames
• 0-8 bytes data length
• Programmable bit rate up to 1 Mbit/sec
• Fully backward compatible with the PIC18XXX8
• Three modes of operation:
• Support for remote frames with automated handling
• Double-buffered receiver with two prioritized
• Six buffers programmable as RX and TX
• 16 full (standard/extended identifier) acceptance
• Two full acceptance filter masks that can be
• One full acceptance filter that can be used as either
• Three dedicated transmit buffers with application
• Programmable wake-up functionality with
• Programmable Loopback mode supports self-test
• Signaling via interrupt capabilities for all CAN
• Programmable clock source
• Programmable link to timer module for
• Low-power Sleep mode
 2011 Microchip Technology Inc.
CAN 2.0A and CAN 2.0B
CAN module
- Mode 0 – Legacy mode
- Mode 1 – Enhanced Legacy mode with
- Mode 2 – FIFO mode with DeviceNet support
received message storage buffers
message buffers
filters that can be linked to one of four masks
assigned to any filter
an acceptance filter or acceptance filter mask
specified prioritization and abort capability
integrated low-pass filter
operation
receiver and transmitter error states
time-stamping and network synchronization
DeviceNet support
ECAN MODULE
TM
data bytes filter support
Preliminary
PIC18F66K80 FAMILY
27.1
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
The CAN module uses the RB2/CANTX and RB3/
CANRX pins to interface with the CAN bus. The
CANTX and CANRX pins can be placed on alternate
I/O pins by setting the CANMX (CONFIG3H<0>)
Configuration bit.
For the PIC18F2XK80 and PIC18F4XK80, the alter-
nate pin locations are RC6/CANTX and RC7/CANRX.
For the PIC18F6XK80, the alternate pin locations are
RE4/CANRX and RE5/CANTX.
In normal mode, the CAN module automatically over-
rides the appropriate TRIS bit for CANTX. The user
must ensure that the appropriate TRIS bit for CANRX
is set.
27.1.1
The CAN bus module consists of a protocol engine,
message buffering and control (see Figure 27-1). 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.
1.
2.
3.
4.
5.
6.
Initial LAT and TRIS bits for RX and TX CAN.
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.
Module Overview
MODULE FUNCTIONALITY
DS39977C-page 395