DCAN250 - Yamar Electronics, Ltd.

Preliminary - Confidential and Proprietary Information of Yamar Electronics Ltd.
Preliminary Description
DCAN250 - CAN over
Powerline Communication
The information in this data sheet is preliminary and may be changed without notice.
1. General
The DCAN250 was designed to transfer CAN messages over noisy DC Power Line using the DCBUS technology. It enables a new physical layer of CAN network for communication between
electronic modules sharing a common DC power supply line. It avoids complex cabling, saves
weight and simplifies installation.
The device receives and transmits CAN2.0A protocol messages. The arbitration over the DC line
is based on the CAN message Identifier's 11 bits. The data is error protected; QPSK modulated
using low voltage narrow band carrier, eliminating the EMC generated by the "square wave" CAN
data lines.
The DCAN250 is implemented in small CMOS digital process allowing integration with other
CMOS IP such as micro-controllers. The DCAN250 is coupled to the DC line via capacitor, thus,
there is no need for high voltage process such as needed by ordinary CAN transceivers.
This innovative solution allows low cost overall CAN implementation, combining power and data
over the same cable, withstanding the hostile DC lines impulse noises.
Main Features
Main Benefits
 CAN A protocol Communication over DC
power line
 Bit rates of up to 250Kbps
 Built-in Modem, Error Correction and
Synchronization
 Multiplex CSMA/CA arbitration mechanism
 Sleep mode for low power consumption
 Eliminates complex harness
 Reduces weight and installation time
 Robust to power line noises
 Increase reliability
 Allows flexible network designs
 Low cost CMOS Implementation
-
Control
Panel
Left Door
ECU
Message A
Message B
Message B
DCAN250
DCAN250
DCAN250
Security
Sensor
Right Door
ECU
Message A
DCAN250
+
Battery
DC BATTERY CABLES
Figure 1 - DCAN250 network example
© 2008-13 Yamar Electronics Ltd.
www.yamar.com
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DCAN 052 Description R0.5
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Preliminary - Confidential and Proprietary Information of Yamar Electronics Ltd.
2. Overview
The DCAN250 network
The DCAN250 operates as part of a network consisting of multiple DCAN250 devices. Each
device can transmit messages to other devices over the power lines according to CAN Host bit
rate (Max 250Kbps). The data on the powerline is phase modulated by a sine wave at a
predefined carrier frequency.
DCAN250 Channel parameters
Channel frequency:
5MHz
CAN data transfer rate:
83.3kbps, 125kbps, and 250kbps
Cable length:
Mainly depends on the power line loads AC [email protected]
DCAN250 Architecture
Passive
Filter
DCAN250
CAN-Tx
CAN
Controller
CAN-Rx
CAN
Protocol
Handling
Transmit
FIFO
Encoder
Decoder
Power
line
Modem
Receive
FIFO
Frontend
Protection
network
Sleep Control
Figure 2 - DCAN250 Block Diagram
The DCAN250 is divided into the following main building blocks;





Protocol handling block, interprets the CAN host protocol.
CODEC block, ECC encodes/decodes the data.
Modem block, phase modulates and demodulates the data to and from the DC-BUS
powerline.
CSMA/CA mechanism allow Carrier sense and arbitration capabilities to the device
Sleep mechanism, ensures low power operation during sleep mode. During Sleep mode,
the device wakes up for short period of time to detect possible wakeup messages from
other devices on the powerline.
DCAN250 Frame Structure
The DCAN250 receives data from its CAN Host. The data is constructed internally into a frame.
The frame starts with a Preamble, followed by data packet and terminated by a “frame end”
indication. When enabled, the DCAN250 message will include in the Preamble, the Carrier Sense
and Arbitration.
© 2008-13 Yamar Electronics Ltd.
www.yamar.com
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DCAN 052 Description R0.5
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Preliminary - Confidential and Proprietary Information of Yamar Electronics Ltd.
3. DCAN250 Protocol
The DCAN250 interfaces to CAN host. The CAN messages are transferred at 83.3kbps, 125kbps
and 250kbps to others DCAN250 over the DC-BUS powerline.
When CAN message is received from the host, the DCAN250 imitates an arbitration sequence
based on the message ID. After gaining access to the powerline, the DCAN250 generate an ACK
and the entire message is transferred to the powerline. If arbitration failed, the DAN250 generates
NACK response to the CAN controller and returns to idle state.
Upon receiving a CAN message from the DC line, the DCAN250 corrects the message from line
errors and transfer it to its CAN controller.
3.1 Bit rate automatic learning
After reset, the first CAN message from CAN controller is used to teach the DCAN250 the CAN
bit rate. The DCAN250 will learn the bit rate and will not send this message over the powerline
nor respond with ACK to this message.
Following messages received from CAN controller are transferred.
The CAN message starts with transmitting an arbitration pattern according to the ID bits in the
CAN message received from CAN controller.
3.2 Constrains
* The CAN controller must wait at least 300u sec between two consecutive messages.
* In case the DCAN250 is receiving a CAN messages from the DC line and at the same time
the CAN controller starts transmitting its CAN message, the DCAN250 will issue a 'dummy'
CAN message with ID '0' and DLC '0' (empty message) to stop the CAN controller message
transmission and 'hold' the CAN bus until the DC line is idle again. In such case, the CAN
controller will lose arbitration and become a receiver. It does not affect transmitter's error
counter. The DCAN250 will repeat issuing the dummy CAN message as long as the DC line is
not idle.
3.3 DCAN250 Timing
SOF
TX CAN MSG
DCAN250 'A' DATA IN
Arb
Powerline FRAME
DCAN250 'B' DATA OUT
Powerline MSG
Ta - 11 bits time (CAN A)
RX CAN MSG
Tb
Ta
Tb - Max time of 360u sec
SOF
Figure 3 - DCAN250 Typical MSG Timing
© 2008-13 Yamar Electronics Ltd.
www.yamar.com
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DCAN 052 Description R0.5
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Preliminary - Confidential and Proprietary Information of Yamar Electronics Ltd.
4. Sleep mode
The device has three power consumption modes: Normal Mode (normal transmitting and
receiving), Sleep Mode (power saving mode), and Standby Mode (after waking up, while pin
nSleep is low). A transition between these modes depends on the sleep control pin, or remotely,
when a Wakeup message is detected on the bus.
During the Sleep mode, the device enters into power saving operation where only its internal low
frequency clock operates. The device wakeup every 32mS for duration of 1.5mS to detect a
dedicated wakeup message on the DC-BUS. If such message is detected, the device switches to
Standby mode, raising its INH pin to indicate its host that a wakeup message has been detected.
It is the responsibility of the host to raise the nSleep pin in order to switch to Normal operation
mode.
Entering Sleep mode
The host can place the device into Sleep mode by a lowering to "0" (falling edge) pin
nSleep .When the device enters to Sleep mode it lowers pin INH.
There are two ways to wakeup the device from Sleep mode.
Wakeup from pin nSleep
In this case, the host wakes the DCAN250 by raising the nSleep pin. The raise the INH pin and
start automatically to transmit the wakeup message.
The device transmits the wakeup message to wakeup all other devices on the DC-BUS. While
transmitting this wakeup message to the DC-BUS, the device lowers pin HDO. After the
transmission is complete the device raises pin HDO (can be used to signal/interrupt the host).
After the transmission is completed and pin nSleep is high, the device enters Normal mode. See
Figure 5 for signals description.
nSleep
HINH
Wakeup Message
Powerline
Normal
Standby
mode
HDO
Figure 4 - Wakeup from nSleep pin
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Preliminary - Confidential and Proprietary Information of Yamar Electronics Ltd.
Wakeup from bus message
During Sleep mode, the device wakes up every 32mS periodically to check for activity on the bus.
If a wakeup message is detected, the device enters Standby mode and raises pin INH. The
device then signals the host by lowering pin HDO for a minimal duration of 8 bits, and a maximal
duration of about 150mSec. The host has to raise nSleep pin (otherwise the device will remain in
Standby mode). After completing the reception, the device enters Normal mode. See Figure 5.1
for signals description.
Wakeup Message
Powerline
msg. detected
DCAN250 Rx
HINH
nSleep
HDO
Standby
Normal mode
Figure 4.1 - Wakeup from bus message
© 2008-13 Yamar Electronics Ltd.
www.yamar.com
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DCAN 052 Description R0.5
Tel: +972-3-5445294 Fax: +972-3-5445279