ANSI CTA-709.3-1999 Free-Topology Twisted-Pair Channel Specification (Formerly ANSI CEA-709.3).pdf

1、 ANSI/CEA Standard Free Topology Twisted-Pair Channel Specification ANSI/CEA-709.3 R-2015 December 1999 NOTICE Consumer Electronics Association (CEA) Standards, Bulletins and other technical publications are designed to serve the public interest through eliminating misunderstandings between manufact

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8、ognizance of the CEA R7 Consumer Electronics Networking Committee.) Published by CONSUMER ELECTRONICS ASSOCIATION 2015 Technology Phone 800-854-7179; Fax 303-397-2740; Internet http:/; Email 3 Network Overview The EIA-709.3 free-topology twisted-pair channel supports up to 128 nodes on a single net

9、work segment with an optional link power source that supplies DC power to the nodes on the network. The channel is specified to support free-topology wiring, and will accommodate bus, star, loop, or any combination of these topologies. The total network length and number of nodes may be extended by

10、use of EIA-709.3 channel physical layer repeaters, or EIA-709.1 compliant routers. The channel data rate is 78.125 kbps. Nodes can be either locally powered or link powered. A link-powered node derives its power from the network. The power is delivered on the same two conductors that carry data. Nod

11、es are polarity-insensitive with respect to data as well as DC power. A locally powered node derives its power from a local source. The data is transmitted using Differential Manchester encoding, which is polarity-insensitive. 4 System Specifications This section specifies the cable type used, termi

12、nations required with bus or free topology, maximum node counts and distances for link and locally powered schemes, and the maximum steady state power that can be drawn from the link power supply. 4.1 Cable The cable shall conform to ANSI EIA/TIA 568A Category 5 requirements for 24 AWG unshielded tw

13、isted-pair cable. For a complete specification, see ANSI/TIA/EIA-568-A-1995. 1 CEA-709.3 4.2 Topology 4.2.1 Free or Bus Topology The network may use either a singly-terminated free topology or a doubly-terminated bus topology. 4.2.2 Repeater Two network segments may be interconnected with an EIA-709

14、.3 channel physical layer repeater. No more than one physical layer repeater shall be in a path between any two nodes on a network. Physical layer repeaters shall not be interconnected in such a way as to create a loop. Each port of a physical layer repeater shall meet the specifications stated in S

15、ections 6.2, 6.3.2, and 6.4. The delay through the repeater shall not exceed 36 s. 4.3 Cable Termination 4.3.1 Free-topology Segment A free-topology segment shall have a single termination. If the segment is locally powered, an RC network as shown in Figure 1 shall be used, with R1 = 52.3 1%, 1/8 W.

16、 The termination may be located anywhere on the segment. If the segment is link-powered, the termination shall be provided by the link power source. See Figure 5. The link power source and termination may be located anywhere on the segment. 4.3.2 Bus Topology Segment A bus topology segment shall hav

17、e two terminations, one at each end of the bus. If the segment is locally powered, an RC network as shown in Figure 1 shall be used, with R1 = 105 1%, 1/8 W at each end. If the segment is link-powered, the link power source shall provide one termination. See Figure 5. The other termination shall be

18、an RC network as shown in Figure 1, with R1 = 105 1%, 1/8 W. C1R1C2+NetworkConnection100F, 50V min100F, 50V minFigure 1 Termination 4.4 Segment Configuration An EIA-709.3 channel shall support up to 128 link-powered or 64 locally-powered nodes at a maximum bit error rate of 1 in 100,000. Both types

19、of nodes shall be supported on a given segment, provided the following constraint is met: (1 x number of link powered nodes) + (2 x number of locally powered nodes) 128 Table 1 shows the maximum bus length for a bus-topology segment. Table 2 shows the maximum node-to-node distance and maximum wire l

20、ength for a free-topology segment. The distance from each node to each of the other nodes and to the link power source shall not exceed the maximum node-to-node distance. If multiple paths exist, e.g., a loop topology, then the longest path shall be used for the calculations. The maximum wire length

21、 is the total amount of wire connected to a network segment. 2 CEA-709.3 Maximum Bus Length Maximum Stub Length Units 600 3 meters Table 1 Bus-Topology Distance Specifications Maximum Node-to-node Distance Maximum Total Wire length Units 250 450 meters Table 2 Free-Topology Distance Specifications 4

22、.5 Power Specifications The sum of the steady-state power drawn by all nodes on a segment shall not exceed 36.5 watts. For each branch, the sum of the products of each nodes distance multiplied by that nodes power shall not exceed a constant: P1*d1+ P2*d2 + P3*d3 + . . . C* where C is a constant, de

23、pendent on wire type, taking into account manufacturing tolerance and all other variations except wire temperature: C = 1.9*103watt-meters; Pi= Node power, i.e., the maximum steady-state power drawn by node i from the network, in watts; di= Node distance, i.e., the distance of node i from the link p

24、ower source, in meters; = 1/(1 + 0.00393*(temp - 25C), accounting for average wire temperature. 5 Link Power A link-powered node derives its power from the network. The power is delivered on the same two conductors that carry data. 5.1 Source The link power source shall consist of a passive coupler

25、together with a power supply having special attributes. The requirements for the power supply for proper system operation include its startup behavior, tolerance to direct shorts across its output, and output voltage regulation. A schematic for the coupler is also included. The combination coupler/p

26、ower supply block diagram is shown in Figure 2. Any deviations from the power supply requirements and coupler schematic (Figure 5) are allowed provided that the link power source design is electrically equivalent. 3 CEA-709.3 Power SupplyLineNeutralEarthA BCouplerVin+EarthVin-Net+Net-CNetworkOutputL

27、ineInputFigure 2 Link Power Source The differential DC output voltage of the link power source shall be 41.0-42.4 VDC over full operating conditions. Under normal (non-fault) conditions, the link power source shall “center“ the output voltage with respect to earth ground, resulting in +21 V and 21 V

28、 outputs at “Net+“ and “Net-“ respectively. The link power source shall recover after a continuous direct short across the output and shall properly restart the EIA-709.3 link powered network. An earth reference terminal is required if the coupler is not grounded via the power supply. 5.2 Power Supp

29、ly Requirements Unless otherwise specified, the power supply specifications in table 3 shall be met over all combinations of the following conditions: Specified coupling circuit connected Line input voltage over full range per specification Network output load = 0 to 1.5 DC amperes 4 CEA-709.3 Descr

30、iption Conditions Specification Line input voltage Phone 800-854-7179; Fax 303-397-2740; Internet http:/; Email; ; OR IEC Central Office, 3, rue de Varembe, PO Box 131, CH-1211 Geneva 20, Switzerland; Phone +41 22 919 02 11; Fax +41 22 919 03 00; Internet http:/www.iec.ch; Email pubinforiec.ch 14 CE

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