Microchip Technology MA330012 데이터 시트
©
2007 Microchip Technology Inc.
Preliminary
DS70165E-page 231
dsPIC33F
20.0
ENHANCED CAN MODULE
20.1
Overview
The Enhanced Controller Area Network (ECAN™)
module is a serial interface, useful for communicating
with other CAN modules or microcontroller devices.
This interface/protocol was designed to allow commu-
nications within noisy environments. The dsPIC33F
devices contain up to two ECAN modules.
module is a serial interface, useful for communicating
with other CAN modules or microcontroller devices.
This interface/protocol was designed to allow commu-
nications within noisy environments. The dsPIC33F
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.
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)
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
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
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.
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.
20.2
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:
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).
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.
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.
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.
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.
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.
(of whatever type) from a following data or remote
frame.
Note:
This data sheet summarizes the features
of this group of dsPIC33F devices. It is not
intended to be a comprehensive reference
source. To complement the information in
this data sheet, refer to the “dsPIC30F
Family Reference Manual” (DS70046).
of this group of dsPIC33F devices. It is not
intended to be a comprehensive reference
source. To complement the information in
this data sheet, refer to the “dsPIC30F
Family Reference Manual” (DS70046).