General Motors Local Area Network (GMLAN) Single Wire Controller Area Network (SWCAN) Physical and Data Link Layers Specification
|Publication Date:||1 January 2015|
This document specifies the physical layer requirements for a Carrier Sense Multiple Access/Collision Resolution (CSMA/CR) data link which operates on a single wire medium to communicate among Electronic Control Units (ECU) on road vehicles at normal transmission rates of 33.333 kbits/s and at a special high speed assembly or service transmission bit rate of 83.333 kbits/s.
This document is to be referenced by the particular Component Technical Specification (CTS) which describes any given ECU in which the single wire data link controller and physical layer interface is located. Only the performance of the data link physical layer is specified in this document. ECU environmental and other requirements shall be provided in the ECU CTS. The intended audience includes, but is not limited to ECU suppliers, Controller Area Network (CAN) controller suppliers, CAN transceiver suppliers, component release engineers and platform system engineers.
Applicability. This specification describes the physical layer requirements for a single wire data link capable of operating with various CSMA/CR protocols such as the CAN version 2.0. This serial data link network is intended for use in applications where high data rate is not required and a lower data rate can achieve cost reductions in both the physical media components and in the microprocessor (μP) and/or dedicated logic devices which use the network.
The network shall be able to operate in either the normal data rate mode or a high speed data download mode for assembly line and service data transfer operations. The high speed mode is only intended to be operational when the bus is attached to an off-board service node. This node shall provide temporary bus electrical loads which facilitate higher speed operation. Such temporary loads shall be removed when not performing download operations.
This physical layer specification includes such transceiver requirements as are necessary to ensure that the bus voltage signals and that a common Integrated Circuit (IC) footprint can be achieved across all applications. The transceiver requirements are specified in Appendix A.
Remarks. This specification is not restricted.