Datasheet

 2009-2012 Microchip Technology Inc. DS70593D-page 201
dsPIC33FJXXXGPX06A/X08A/X10A
19.0 ENHANCED CAN (ECAN™)
MODULE
19.1 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
dsPIC33FJXXXGPX06A/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 eight transmit buffers with application speci-
fied 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
• Three 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, or remote transmission
requests initiated by the user, 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 also includes an extended identifier.
• 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 two
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 fea-
tures of the dsPIC33FJXXXGPX06A/
X08A/X10A family of devices. How-
ever, it is not intended to be a compre-
hensive reference source. To
complement the information in this data
sheet, refer to Section 21. “Enhanced
Controller Area Network (ECAN™)”
(DS70185) in the “dsPIC33F/PIC24H
Family Reference Manual”, which is
available from the Microchip web site
(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.