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 1 DCAN 052 Description R0.5 Tel: +972-3-5445294 Fax: +972-3-5445279 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 impedance.@5MHz. 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 2 DCAN 052 Description R0.5 Tel: +972-3-5445294 Fax: +972-3-5445279 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 3 DCAN 052 Description R0.5 Tel: +972-3-5445294 Fax: +972-3-5445279 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 © 2008-13 Yamar Electronics Ltd. www.yamar.com 4 DCAN 052 Description R0.5 Tel: +972-3-5445294 Fax: +972-3-5445279 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 5 DCAN 052 Description R0.5 Tel: +972-3-5445294 Fax: +972-3-5445279