1、 ANSI/CEA Standard Free-Topology Twisted Pair Channel Specification ANSI/CEA-709.3-R2004 December 1999 NOTICE Consumer Electronics Association (CEA) Standards, Bulletins and other technical publications are designed to serve the public interest through eliminating misunderstandings between manufactu
2、rers and purchasers, facilitating interchangeability and improvement of products, and assisting the purchaser in selecting and obtaining with minimum delay the proper product for his particular need. Existence of such Standards, Bulletins and other technical publications shall not in any respect pre
3、clude any member or nonmember of CEA from manufacturing or selling products not conforming to such Standards, Bulletins or other technical publications, nor shall the existence of such Standards, Bulletins and other technical publications preclude their voluntary use by those other than CEA members,
4、 whether the standard is to be used either domestically or internationally. Standards, Bulletins and other technical publications are adopted by CEA in accordance with the American National Standards Institute (ANSI) patent policy. By such action, CEA does not assume any liability to any patent owne
5、r, nor does it assume any obligation whatever to parties adopting the Standard, Bulletin or other technical publication. This CEA Standard is considered to have International Standardization implication, but the International Electrotechnical Commission activity has not progressed to the point where
6、 a valid comparison between the CEA Standard and the IEC document can be made. This Standard does not purport to address all safety problems associated with its use or all applicable regulatory requirements. It is the responsibility of the user of this Standard to establish appropriate safety and he
7、alth practices and to determine the applicability of regulatory limitations before its use. (Formulated under the cognizance of the CEAs R7.1 HCS1 Subcommittee) Published by CONSUMER ELECTRONICS ASSOCIATION 2004 Technology Phone 800-854-7179; Fax 303-397-2740; Internet http:/; Email 3 Network Overv
8、iew The EIA-709.3 free-topology twisted-pair channel supports up to 128 nodes on a single network 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 comb
9、ination of these topologies. The total network length and number of nodes may be extended by 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 p
10、ower from the network. The power is delivered on the same two conductors that carry data. Nodes 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 po
11、larity-insensitive. 4 System Specifications This section specifies the cable type used, terminations 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
12、The cable shall conform to ANSI EIA/TIA 568A Category 5 requirements for 24 AWG unshielded twisted-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-termi
13、nated bus topology. 4.2.2 Repeater Two network segments may be interconnected with an EIA-709.3 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 cr
14、eate a loop. Each port of a physical layer repeater shall meet the specifications stated in Sections 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
15、 locally powered, an RC network as shown in Figure 1 shall be used, with R1 = 52.3 1%, 1/8 W. 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
16、 located anywhere on the segment. 4.3.2 Bus Topology Segment A bus topology segment shall have 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 l
17、ink power source shall provide one termination. See Figure 5. The other termination shall be 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
18、-powered or 64 locally-powered nodes at a maximum bit error rate of 1 in 100,000. Both types 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 f
19、or a bus-topology segment. Table 2 shows the maximum node-to-node distance and maximum wire length 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 loo
20、p topology, then the longest path shall be used for the calculations. The maximum wire length 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 M
21、aximum Total Wire length Units 250 450 meters Table 2 Free-Topology Distance Specifications 4.5 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
22、 power shall not exceed a constant: P1*d1+ P2*d2 + P3*d3 + . . . C* where C is a constant, dependent 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
23、i from the network, in watts; di= Node distance, i.e., the distance of node i from the link power 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 con
24、ductors that carry data. 5.1 Source The link power source shall consist of a passive coupler 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 outpu
25、t voltage regulation. A schematic for the coupler is also included. The combination coupler/power 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 equiv
26、alent. 3 CEA-709.3 Power SupplyLineNeutralEarthA BCouplerVin+EarthVin-Net+Net-CNetworkOutputLineInputFigure 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 sourc
27、e shall “center“ the output voltage with respect to earth ground, resulting in +21 V and 21 V 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 refer
28、ence terminal is required if the coupler is not grounded via the power supply. 5.2 Power Supply 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
29、over full range per specification Network output load = 0 to 1.5 DC amperes 4 CEA-709.3 Description 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
30、+41 22 919 02 11; Fax +41 22 919 03 00; Internet http:/www.iec.ch; Email pubinforiec.ch 14 CEA Document Improvement Proposal If in the review or use of this document, a potential change is made evident for safety, health or technical reasons, please email your reason/rationale for the recommended change to standardsce.org. Consumer Electronics Association Technology & Standards Department 1919 S Eads Street, Arlington, VA 22202 FAX: (703) 907-7693 standardsCE.org
