TOKYO Hoping to influence the standards process for long-distance IEEE 1394 networks, NEC Corp. has introduced a physical-layer chip and has prototyped a bridge device that it says will enable 1-km networks. The company will be at the 1394 Developer's Conference in San Jose, Calif., next week to show a prototype wiring concentrator based on a demonstration board that houses the new devices.
The physical-layer chip and a 250-Mbit/second transceiver module for plastic optical fiber began sampling this week. The PHY chip, designated the PD72880, is capable of 400 Mbits/s.
"Our [solution] includes all essential technologies necessary to implement 1394 for long-haul applications. We want to propose these technologies to the standards body," said research manager Shuntaro Yamazaki at NEC's Access Network Technology Group.
The physical-layer chip is fully compliant with P1394b draft specifications, but there is still a mountain of issues that have not been resolved by the working group overseeing the spec, Yamazaki said. NEC claims its architecture is superior in addressing signal delay and thus is capable of 500-meter transmission a fivefold improvement over the P1394b requirement. The chip also supports full-duplex transmission as required by the specification.
"We introduced a full-duplex system based on 1394b. The current 1394a is based on a half-duplex system, which yields a maximum transmission distance of 4.5 meters," Yamazaki said.
The chip has three operating modes 400, 200 and 100 Mbits/s enabling it to connect to transceivers for glass optical fiber, plastic optical fiber and UTP5 unshielded twisted-pair cable. The device is also said to guarantee backward compatibility with current link layers, protocols and applications by conforming to IEEE-1394-1995 P1394a Draft 2.0. System designers can therefore develop a long-haul 1394 system using an existing 1394 environment.
For wireless infrared networks using 1394, the device has an echo-detection function that prevents unnecessary bus resets.
The NL2110 transceiver module is intended for plastic optical fiber. It allows transmission speeds of 250 Mbits/s and enables distances up to 50 meters using low-cost plastic optical fiber.
Full production of the devices is scheduled to begin in September. The physical layer comes in a 144-pin low profile quad flat pack and runs off a 3.3-V power supply. The transceiver module comes in a one- by nine-pin standard SIP and operates with a 5-V power supply. Sample prices are about $25 for the PHY and about $42 for the transceiver module.
NEC also hopes to drive standards with its prototype network concentrator. "We have taken in all technologies that are being discussed by the P1394.1 Working Group and added our technologies to realize 1394 bridging," Yamazaki said.
IEEE 1394 features plug-and-play capability. But when a device is connected to a 1394 network, a "bus reset" shuts down a signal flow across the network and all connected networks as well. That can cause, for example, video dubbing to be cut off when some other device is connected to the network.
The maximum number of devices to be hooked to a 1394 network is 63, which is not enough for professional use networks, Yamazaki said. To avoid saturation of the network, efficient data traffic control is needed. The IEEE 1394 protocol also limits transmission distances to about 500 meters of cable.
NEC said its prototype link-layer chip, called Malco, addresses those problems. The prototype Malco board packs that chip along with the physical-layer device and the transceiver module in an implementation called Portalgear. Although the P1394.1 bridge specification is still under discussion, Portalgear includes the technologies being weighed for P1394, in addition to proprietary NEC technologies.
The Malco chip for hardware-based routing enables maximum throughput of 128 Mbits/s, corresponding to simultaneous four-channel DV-format video transmission. It also comprises an NEC-developed bus-clock synchronization scheme for complete compatibility with legacy 1394 equipment.
NEC allowed for automatic dynamic network configurability to ensure plug-and-play capability over multiple bridges. With the PD72880 PHY, Portalgear is claimed to enable 1394 transmission to 1 km.
NEC says it plans to integration all Malco board chips into a system-on-chip within two years.