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CAN partial networking & CAN FD

IP.com Disclosure Number: IPCOM000213467D
Publication Date: 2011-Dec-15
Document File: 6 page(s) / 57K

Publishing Venue

The IP.com Prior Art Database

Related People

Elend, Bernd: INVENTOR [+2]

Related Documents

CAN with Flexible Data-Rate: OTHER

Abstract

A CAN transceiver according to ISO11898-6 will wake-up if a certain amount of CAN FD frames occur on the bus. The wake-up happens due to error counter overflow in the transceiver which prevents that nodes that do not support CAN FD can remain in sleep/standby mode, while others that are capable of transmitting/receiving CAN FD frames make use of this new CAN protocol feature. It is proposed that, to overcome this problem, the error counter in the transceiver can be configured to be disabled for CAN FD frames , preferably only temporarily until the next idle phase when the transceiver detects that the EDL bit has been received recessive.

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Page 01 of 6

TR1150

CAN partial networking & CAN FD


8 December 2011

Technical Report

Document information

Info

Content

Title

CAN partial networking & CAN FD

Author(s) Bernd Elend

Department Systems & Applications (AIC)

Keywords CAN FD, ISO11898-6


Page 02 of 6

  TR1 150

NXP Semiconductors

Systems & Applications

Summary

This document describes the implications of using CAN transceivers that are designed to conform to NWIP/ISO11898-6 in CAN FD systems. Furthermore strategies are described how the selective wake-up function can be maintained in a CAN-FD system

TR1150

© NXP B.V. 2011. All rights reserved.

Technical Report


8 December 2011

2 of 6


Page 03 of 6

NXP Semiconductors

TR1150

Systems & Applications


1. Introduction


1.1 ISO11898


1.1.1 ISO11898-1

This ISO standard describes the "Controller Area Network" (CAN) protocol, which is widely used in automotive and industrial applications. Data transfer with a bitrate of up to 1Mbps and maximum 8 bytes of data per message are the basic limitations of this protocol.


1.1.2 ISO11898-2 / ISO11898-5

These ISO standards describe the physical layer that is used for transmitting CAN messages. Part 2 defines the basic parameters. Part 5 adds a low power mode with wake-up functionality. This wake-up function is implemented in such way, a wake-up happens upon reception of any message.


1.1.3 NWIP/ISO11898-6

A new part of the ISO11898, part 6, defining selective wake-up functionality is currently under development. (http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=59165).

Here, ISO11898-6 and NWIP/ISO11898-6 are used interchangeably to refer to this expected new part of the standard.

Here a wake-up of the physical layer devices happens upon a predefined wake-up message, which in turn requires a CAN protocol decoder in the physical layer chip.

The ISO11898-6 considers only CAN messages according ISO11898-1.

1.2 In case the physical layer chip according to ISO11898-6 receives a message that cannot be decoded properly an error counter shall be incremented. The error counter is decremented, when a message has been decoded without errors. Overflow of the error counter shall lead to a wake-up. The assumption is that decoding errors are a result of wrong bit timing configuration or a decoder clock out of spec.CAN FD

CAN FD is a new proposal from Bosch to overcome the limitations of the CAN protocol,


i.e. to allow more than 8 bytes of data per frame and also to increase the (average) gross bitrate above 1Mbps. ( http://www.semiconductors.bosch.de/media/pdf/canliteratur/can_fd.pdf)

This extension of the CAN protocol requires a new CAN decoder. While the new CAN FD decoder is able to send and receive ISO11898-1 conforming CAN messages, the 'old- fashioned' CAN controller is neither able to send nor to receive CAN FD messages.

The ISO11898-1 CAN controller would send error frames upon reception of CAN FD messages and prevent the CAN FD communication.

TR1150

© NXP B.V. 2011. All rights reserved....