IEEE 1394 Basic Requirements

The following is a summary of the IEEE 1394 design considerations related to PC systems, as addressed in this chapter:

Compliance with various approved IEEE 1394 standards
Support for the OpenHCI specification for controllers
Plug and Play support for device configuration, control and status registers (CSRs), connectors and cabling, and connection fault handling
Cable power distribution, including requirements for source devices, sink devices, self-powered devices, and supporting CSRs
Device power management, CSRs, and soft-power protocols
Device command protocols for audio, video imaging, still imaging, and storage device classes

This section defines the basic PC 98 requirements for IEEE 1394.

1. Controllers and devices support IEEE 1394-1995 standards

Required

Designs that interface to the IEEE 1394 bus must support the following industry standards and supplemental specifications:

IEEE 1394-1995 standard
IEEE 1394A, an amendment to IEEE 1394-1995
IEEE 1212-1991 CSR Format (ISO/IEC 13213:1994)

2. Controllers comply with OpenHCI for IEEE 1394

Required

The OpenHCI specification for IEEE 1394 defines standard hardware and software for PC connections to the IEEE 1394 bus. OpenHCI defines standard register addresses and functions, data structures, and DMA models. The benefits of this standard include improved performance, security, and error handling.

An IEEE 1394 OpenHCI device is bus manager-capable, including bus mastering for BANDWIDTH_AVAILABLE and CHANNELS_AVAILABLE registers.

3. OpenHCI controllers and devices support advances defined in IEEE 1394A

Required

The advances in the IEEE 1394A specification enhance system performance and integration of component systems.

4. Host supports peak data rate of 400 Mb/s, minimum

Required

The integration of component systems that enable concurrent applications demands minimum bandwidth for an effective user experience. A peak data rate of 400 Mb/s is required for effective integration of systems and devices targeted for use with PCs in 1998.

5. Design avoids excessive currents resulting from ground-fault potential among devices

Recommended

PC-based peripherals are not required to implement isolation because of the usual assumption of a common green-wire ground for all linked devices. Accordingly, the requirement for electrical isolation has been targeted for removal from the IEEE standard.

For local area network (LAN) configurations, it is desirable to avoid excessive currents resulting from ground-fault potential among devices. The related design problem can be solved for such configurations by building isolation into the power supply and by AC coupling of the physical layer device (PHY) and Link interface of selective AC-powered subsystems.

Notice that a mobile device powered by AC is considered to be an AC device, even with a battery (DC) present. The PC uses this level of definition to budget cable power.