VersaPHY Ready for the In-Vehicle Network

Contributed by:
Richard Mourn
Quantum Parametrics

The new 1394 Automotive standard will move FireWire forward as a preferred specification for entertainment and information systems in the vehicle.  One of the options available now for automakers and their suppliers is the VersaPHY architecture. VersaPHY is a backward-compatible extension to IEEE-1394, which allows simple applications to connect simply (no device software required) to an IEEE-1394 bus.  It capitalizes on the IEEE-1394b-2002 (beta) PHY layer which allows long haul (100m), high speed (4Gb/s), and low latency coupled with the flexible topology configurations of daisy-chain, tree, star and redundant loops, and has been proven in networking, industrial, aerospace, and military applications.  And now it’s an option for the vehicle.

The VersaPHY architecture model includes one or more controllers plus one or more VersaPHY devices, which incorporate a register set and simplified management logic. (In contrast, USB is not equipped to divide the master control function among multiple nodes when needed for reliability, scalability, or any other purpose.) The architecture connects the 1394 PHY directly to a specific application, removing the asynchronous transaction requirements from simple asynchronous and streaming devices and replacing them with a much simpler set of VersaPHY requirements. This architectural change allows devices such as sensors, actuators, cameras, speakers, microphones, and similar products to be created without a link controller, 1394 transaction software or a microprocessor. VersaPHY reduces or even eliminates the 'device discovery' process, and its corresponding software, thereby simplifying control and data delivery functions.

VersaPHY includes new facilities such as VersaPHY labels, which are used as permanent or semi-permanent addressable names for devices, and in more complex implementations, as names for multiple profiles within a device. Another key enhancement is the creation of writeable PHY registers, enabling PHY-only devices to initiate transaction-like communication. The enhancement will simplify the use of 1394 and eliminate the cost of implementing transaction-capable nodes in mass-market, cost-sensitive applications.

VersaPHY is already seeing success in areas such as cameras, GPIO and bridging legacy I/Os to 1394. Pre-assigned VersaPHY labels are ideal for closed systems were the installer can guarantee a specific device or device function are present and have the same VersaPHY label every time. This sharply reduces the complexity of the device discovery process and increases reliability.

Automotive companies are using IEEE-1394 for entertainment, navigation and collision detect systems. This places 1394 cabling next to other automotive components that need to be controlled but currently use a separate control bus, which increases cable and connector weight and costs. VersaPHY's simplicity allows these applications to take advantage of the 1394 cabling while being controlled through a very simple and many times similar protocol approach using VersaPHY.

For example, in an automobile seat often there is a need for a high speed interface for a rear seat display plus basic functions such as seat positioning, cooling/heating, seat belt sensors and lumbar support. With 1394 and its 100% compatible VersaPHY extension, these simple devices share the same cable as the high speed device, thus reducing wire harness complexity and costs. The VersaPHY device monitors the sensors and notifies the controller when conditions change, and the VersaPHY registers can be written by the controller to drive the actuators. This capability enables a significant cost reduction because a simple low-cost 1394 connection for items like seats can be located on the same 1394 network used for infotainment.