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General FAQ
1394 Isolation FAQ
Designer Kits FAQ
Link Layer Devices FAQ
Physical Layer Devices FAQ
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General 1394 FAQ
| Q1: How can I get a copy of the IEC61883 specififcation? |
As of February '98, the IEC61883 spec is official, it can be ordered through the IEC. However, the IEC 61883 specification is actually part of a bigger specification of the Audio Video Consortium referred to as the "Blue Book." Please see  http://www.1394ta.org/abouttech/bluebk.html for ordering information |
| Q2: What is the role of the Isochronous Resource Manager? |
| The isochronous resource manager (IRM) provides a means for nodes to cooperatively share isochronous resources on the bus. The IRM must handle the bandwidth available and channel available registers. See section 8.4.2.3 of the IEEE 1394-1995 for determination of IRM and section 8.3.1.6 for responsibilities of an IRM. |
| Q3: What is the role of the Bus Manager? |
| The Bus Manager must collect the self-id packets and create the topology and speed maps from them. Depending on the FIFO sizes, the collection of the self-id packets can be a problem if the bus has a lot of nodes. See section 8.4.2.5 of the IEEE 1394-1995 standard for determination of the Bus Manager and section 8.3.1.6 for responsibilities of a Bus Manager.
All of TI’s 1394 devices are fully Bus Manager compliant. All of the embedded software available from TI for the TSB12LV31 and TSB12LV41 are Bus Manager enabled. |
| Q4: Who assigns the bus ID for a given node? |
| The bus ID is assigned by software. If a bus bridge exists, the bus ID can be set by the Bus Manager to whatever value the Bus Manager gets from the bus bridge. If no bus bridges exist the default bus ID is 3F (local bus) per the 1394-1995 standard. See section 8.3.2.2.3 of the IEEE 1394-1995 standard for more information. |
| Q5: What should a 1394 device that is not Bus Manager, IRM, or Cycle Master capable and send isochronous packets do if its node becomes root? |
| Only the Bus Manager (or IRM if no Bus Manager is on the bus) may force a node to become root. If there is no IRM capable node on the bus, then the 1394 node described should not send isochronous packets.
The only reason a node would not want to be root is that it does not want to be Cycle Master. See paragraph 8.4.2.6 of the IEEE 1394-1995 standard to understand how the Cycle Master is selected.
The Bus Manager (or IRM if a bus manager is not present) will find a node capable of being Cycle Master. It will then send a PHY configuration packet to force that node to become root and cause a bus reset. It will then set the cmstr bit in the STATE_CLEAR register of the root node to turn on the Cycle Master. Of course a node that is IRM capable will also be Cycle Master capable and may make itself root.
There is no way for a node to cause itself not to be root. There is a way to force a node to become root by setting the RHB (Root Holdoff Bit) with a PHY configuration packet and then initiating a bus reset. If your node always becomes root, then for some reason your PHY is slower than the other PHYs on the bus. |
| Q6: Where can I get a copy of the IEEE 1394-1995 specification? |
| Q7: Who is manufacturing the cable and connectors? |
Molex, Joinsoon, and many others.
Molex, Inc. Joinsoon
2222 Wellington Ct. 2322 S. Pullman St.
Lisle, IL 60532 Santa Ana, CA 92705
708-969-4490 714-261-3403
Attn: S.Y. Theng Attn: Rick Foringer
Molex Worldwide Contacts:
Europe : H.T. Leong Ph: 31-40-258-3180
Japan : Shinichi Tadokoro Ph: 81-462-61-4500
S.E. Asia: Kok Whee Teo Ph: 65-268-6868
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| Q8: What 1394 connector specifications are available? |
The connector specifications are located in the IEEE 1394-1995 standard. This document contains both cable as well as connector mechanical drawings. |
| Q9: What is the maximum transmission rate? |
| 1394-1995 is defined to support - 100, 200, and 400 m/bits per second data throughput rates. The committee decided to define these speeds up front so that future speed enhancements can be quickly implemented. There are efforts to expand the standard to include 800 and multi-Gigabit speed improvements in 1394B. |
| Q10: Is the transfer rate of the 1394 scalable? |
| Yes, 100, 200, and 400 megabits per second nodes can all be supported in the same topology. |
| Q11: Will this require a different chip set for each speed? |
| No. A 400Mbps chipset will support 400 Mbps, 200 Mbps, and 100Mbps. Similiarly a 200 Mbps chipset will support communication with itself and other nodes at 200 and 100 Mbps, but not 400Mbps. Finally a chipset designed to only 100 Mbps will not be able to receive or transmit 200 Mbps or 400Mbps packets. 1394 is designed to allow different rate nodes on a single bus, so there is no requirement to have every node capable of operation at all speeds. If you add a new node, the topology will reconfigure itself to incorporate the new node at its maximum capable speed. |
| Q12: How does the sustainable bandwidth differ between isochronous and asynchronous transactions? |
| The two major differences between the two types of transaction which affect the sustained throughput are that isochronous transactions do not involve 'acknowledges' and isochronous gaps are of shorter duration than 'subaction gaps'. |
| Q13: How many power lines are incorporated in the 1394 cable? |
| There are two power lines that are used in the 1394 cable. |
| Q14: What type of cable is used with 1394? |
| It is a six wire, shielded twisted-pair cable. |
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