1、NCITS Technical Report NCITS TR-23-1998 Information Technology - SCSI Enhanced Parallel Interface (EPI) Developed by the National Committee for Information Technology Standards (NCITS) This material is reproduced from American National Standard , copyright 1% , with permission of the American Nation
2、al Standards Institute, Inc. Not for resale. No part of this publication may be copied or reproduced in any form, electronic retrieval system or otherwise, without the prior written permission of the American National Standards Institute, Inc., 11 West 42nd Street, New York, New York 10036. c STD-AN
3、SI TR-23-ENGL 1198 072q150 0553205 727 NCITS TR-23-1998 NCITS Technical Report Information Technology - SCSI Enhanced Parallel Interface (EPI) Secretariat Information Technology Industry Council Abstract This technical report describes SCSI configurations that may be achieved within the context of t
4、he specifi- cations in the SCSIQ, SCSI-3 SPI, SCSI-3 Fast-20, and SPI-2 standards. These configurations have one or more configuration parameters expanded beyond that documented in the standard documents and may require special components, special restrictions, or an interpretation of the underlying
5、 technical reasons for parameters specified in the standards. This technical report describes the considerations that can lead to effective implementations of special components but does not describe the detailed design of any com- ponent. The information in this technical report does not supersede
6、any requirements in the referenced standards. STD-ANSI TR-23-ENGL 1998 m 07211150 055120b bbb m NCITS Tech n ica This Technical Report is one in a series produced by the National Committee for Information Technology Standards (NCITS). The secretariat for NCITS is held by I the Information Technology
7、 Industry Council (ITI), 1250 Eye Street, NW, Suite 200, As a by-product of the standards development process and the resources of knowledge devoted to it, NCITS from time to time produces Technical Reports. Such Technical Reports are not standards, nor are they intended to be used as such. Report W
8、ashington, DC 20005. Series NCITS Technical Reports are produced in some cases to disseminate the technical and logical concepts reflected in standards already published or under development. In other cases, they derive from studies in areas where it is found premature to develop a standard due to a
9、 still changing technology, or inappropriate to develop a rigorous standard due to the existence of a number of viable options, the choice of which depends on the users particular requirements. These Technical Reports, thus, provide guidelines, the use of which can result in greater consistency and
10、coherence of infomation processing systems. When the draft Technical Report is completed, the Technical Committee approval process is the same as for a draft standard. Processing by NCITS is also similar to that for a draft standard. PATENT STATEMENT CAUTION: The developers of this Technical Report
11、have requested that holders of patents that may be required for the implementation of the Technical Report, disclose such patents to the publisher. However, neither the developers nor the publisher have undertaken a patent search in order to identify which, if any, patents may apply to this Technica
12、l Report. As of the date of publication of this Technical Report and following calls for the identification of patents that may be required for the implementation of the Technical Report, no such claims have been made. No further patent search is conducted by the developer or the publisher in respec
13、t to any Technical Report it processes. No representation is made or implied that licenses are not required to avoid infringement in the use of this Technical Report. Published by American National Standards institute 11 West 42nd Street, New York, New York 10036 Copyright O 1999 by Information Tech
14、nology Industry Council (ITI) All rights resewed No part of this publication may be reproduced in any form, in an electronic retrieval system or otherwise, without prior written pennission of the publisher. Printed in the United States of America . STDmANSI TR-23-ENGL 3778 = 072LI350 0553207 5T2 M C
15、ontents 1 . Scope 6 2 . References 7 2.1 Approved references . 7 2.2 References under development 7 2.3 Other references . 8 3 . Definitions. symbols. and abbreviations 8 3.1 Definitions . 8 3.2 Abbreviations and symbols . 9 4 . General . 10 5 . Bus model . 10 5.1 Bus related terminology and concept
16、s 10 5.2 SCSI domain related terminology and concepts . 14 Page 6 . Bus segments in a SCSI domain 15 7 . SCSI bus segments 15 7.1 Segment length parameters 15 7.1.1 Protocol timing limits 16 7.1.1.1 Device loading parameters . 17 7.1 . 1 . 2 Caution when using HVD interfaces (separate transceivers)
17、17 7.1.2 Propagation - time - limited domain length . 17 7.1.3 Signal quality limits . 18 7.1.4 Printed circuit board parameters 19 8 . Bus segment guidelines 20 8.1 Bus segment loading . 20 8.2 Maximum speed of operation 21 8.4 Comments on the segment length rules . 23 9 . Mixed width operation . 2
18、7 9.1 16-bit main path 27 9.1.1 Async. Fast-5, Fast-10, and Fast-20 cases . 27 9.1.2 Fast-40 case 29 9.2 8-bit main path 29 9.3 Single 16-bit path and single 8-bit path . 31 9.4 Multiple 8 or 16-bit paths . 31 1 O . Bus expanders 34 10.1.1 Homogeneous iype 36 10.1.3 Domain examples using simple expa
19、nders 36 10.1.4 General rules for SCSI domains using simple expanders 37 10.1.4.1 Rule summary . 37 7.2 Other segment properties . 19 8.3 Other segment guidelines . 22 8.5 Segment length tables 24 10.1 Simple expanders . 34 10.1.2 Heterogeneous types . 36 Page 1 . STD-ANSI TR-23-ENGL 3918 0724350 05
20、53208 439 Page 10.1.4.2 Rule 1 38 10.1.4.3 Rule 2 38 10.1.4.4 Rule 3 40 10.1.4.4.1 Effects of wired-or glitches . 40 10.1.4.4.2 Effects of slow response to BUS FREE . 40 10.1.4.4.3 Expander propagation delay effects . 41 10.1.4.4.4 Sample calculations . 42 10.1.4.5 Rule 4 44 10.1.4.6 Rule 5 44 10.1.
21、4.7 Rule 6 (REGYACK offset) 45 10.2 Bridging expanders . 47 10.2.1 Two-port caching expanders 47 10.2.2 Logical unit bridges 48 10.2.3 Unsupported configurations . 51 10.2.3.1 Case 2 . 51 10.2.3.2 Case 3 . 51 10.2.4 Switching expanders 52 11 . Dynamic reconfigurations of domains . 55 11.1 Addition a
22、nd removal of devices . 55 11.1.1 Framework for device addition and removal process . 55 1 1.1.1.1 End states and other terminology . 55 1 1.1.1.2 Hot-plugging process 56 11.1.1.3 Framework for incoming object devices 56 11.1.1.4 Framework for outgoing object devices 57 11.1.2 Electrical considerati
23、ons for device insertion and removal 57 11.1.2.1 Insertion 57 11.1.2.2 Removal 61 11.1.3 Logic input states during transitions - stage 7 detection 61 1 1.1.4 Operational state changes for devices . 62 11.2 Reconfiguration of bus segments 62 11.2.1 Addition and removal of bus segments 62 11.2.2 Opera
24、tional state changes for segments . 65 12 . Topologies and configuration rules for dynamically reconfigurable domains 65 13 . Terminator power distribution within a segment 65 13.1 Wire effects . 66 13.1.1 SE 67 13.1.2 LVD 68 13.1.3 LVD/MSE . 69 13.1.4 HVD 69 13.2 Mixed power configurations 69 13.3
25、TERMPWR source placement 69 14 . Grounding and ground distribution 70 14.1 SE systems . 72 14.2 Differential systems . 72 14.3 Shield connections 72 14.4 System considerations: . 73 14.4.1 Ground paths in the SCSI cable . 73 14.4.2 Building power distribution . 74 Page 2 Page 14.4.3 Ground loops 75
26、15 . Interconnects . 76 15.1 Connectors 77 15.2 Connection srpes . 77 15.3.1 SE . 78 15.3 Connections covered . 78 15.3.2 HVD 78 15.3.3 LVD 78 15.5 68-position bus segment termination 79 15.5.2 Specific precautions . 80 15.6 Rack mount considerations . 80 15.7 Tables for specific combinations . 81 1
27、5.4 Cross Reference . 79 15.5.1 General applications . 79 Page 3 STD-ANSI TR-23-ENGL 3778 0724350 0553230 O97 Page TABLE OF FIGURES Figure 1 . Single segment physical architecture and terminology examples 14 Figure 2 . Mixed width connections using 16-bit main path 28 Figure 3 . Mixed width connecti
28、ons using 8-bit main path 30 Figure 4 . Mixed width using a cingle 8-bit and a single 16-bit path . 31 Figure 5 . Mixed width configuration with two 8-bit paths and one 16-bit path . 32 Figure 6 . Mixed width configuration with two 16-bit paths . 33 Figure 7 . A two segment domain using a single exp
29、ander circuit 35 Figure 8 . Three ways to couple bus segments together with expanders . 35 Figure 9 . Examples of domains using simple expanders . 37 Figure 10 . Intermediate segments and performance ranking 39 Figure 11 . Explanation of the 300 ns domain limit caused by Figure 12 . Two configuratio
30、ns for domain delay calculations 43 Figure 13 . Examples of illegal loops 44 Figure 14 . General bridging expander . 47 Figure 15 . Case 1 LUN bridge architecture . 49 Figure 16 . Unsupported Case 2 configuration . 51 Figure 17 . Unsupported Case 3 configuration . 52 Figure 18 . One set of data path
31、s in a SCSI switch 53 1800 ns BUS-SET-DELAY . 41 Figure 19 . Another set of data paths in the same SCSI switch 54 Figure 20 . Stages O thru 3 for the insertion process 58 Figure 21 . Stages 4 thni 7 for the insertion process 58 Figure 22 . Dynamic addition / removal of a bus segment 63 Figure 23 . E
32、xamples of various ground points . 71 Figure 24 . Shield connection details 73 Figure 25 . Basic single phase power distribution system 74 TABLE OF TABLES Table 1 . Length limits for SE bus segments 24 Table 2 . Length limits for HVD bus segments 25 Table 3 . Length limits for LVD bus segments 26 Ta
33、ble 4 . Performance ranking for intermediate segments . 38 Table 5 . Domain delay calculations . 43 Table 6 . Minimum REWACK offset levels for maximum performance 45 Table 7 . Typical TERMPWR source voltages 67 Page 4 STD.ANS1 TR-23-ENGL 1778 072Li15O 05512LZ T23 D Page Table 8 . TERMPWR SE bus segm
34、ent length limits . 68 Table 9 . Supported combinations 79 Table 1 O . SE: contact assignments . A-cable 81 Table 11 . HVD: contact assignments . A-cable 82 Table 12 . LVD: contact assignments . A-cable 83 Table 13 . SE: contact assignments . P-cable 84 Table 14 . HVD: contact assignments . P-cable
35、85 Table 15 . LVD: contact assignments . P-cable 86 Table 16 . SE: contact assignments for 80 position SCA-2 . 87 Table 17 . HVD and LVD: contact assignments for 80 position SCAQ . 88 Table 18 . SE: 68-position connector see SAM-2. Terminator: Interconnect components that form the ends of the transm
36、ission lines in bus segments. A SCSI domain (5.2) has at least one segment and at least two terminators (except for special cases where the electrical transmission lines are very short). Terminators bias the signals on a bus segment to the false state. This ensures a false state when no devices are
37、driving. Terminators also minimize signal reflections. Bus segment types: There are presently three types of SCSI bus segment: 0 Single ended (.e., monomode single ended (SE) or multimode single ended (MSE) High voltage differential (HVD) 0 Low voltage differential (LVD) The bus segment type is dete
38、rmined by the properties of the terminators used. Devices that do not have the same transceiver type as the terminators cannot operate in the segment defined by the terminators. Bus-path: The electrical connection directly between the two terminators in a bus segment Stub: Any electrical path in a b
39、us segment that is not part of the bus-path Page 11 STD-ANSI TR-23-ENGL 1778 D 0724150 0553238 388 D EPI Rev 16 Stub connection: The point where a stub meets the bus-path Transmission medium (media): An electrical conductor having bus termination on each end and possibly stubs Common examples of med
40、ia are cables, printed wiring boards, backplanes, flex circuits, and connectors that create the electrical connections between SCSI devices and/or bus expanders (see below) and terminators. SCSI bus (segment) connector: Any connector used to create a SCSI bus segment SCSI bus connectors are defined
41、both by their function AND by their physical placement. There are only two allowed functions: bus-path and stub. There are numerous physical placement descriptions. Examples of SCSI bus connectors are “ device stub connector“ and “ terminator bus-path connector“ . Bus-path connector (functional desc
42、ription): Any connector used to provide part of the bus-path Stub connector (functional description): Any connector used to provide part of a stub Device connector (physical placement description): Any connector physically part of a SCSI device Cable connector (physical placement description): Any c
43、onnector that is physically part of a cable assembly, attached to backplanes, or other non-device conductors Terminator connector (physical placement description): Any connector physically part of a terminator It is not uncommon for terminators to have both stub and bus-path connectors (see Figure 1
44、). Page 12 EPI Rev 16 Enclosure connector (physical placement description): Any connector that is physically part of an enclosure Note: The above list of physical placement descriptions contains examples and is not intended to be complete. Other physical placement descriptions may be used. Note conc
45、erning the location of the stub connection point: The mating interface of stub connectors is considered to be the stub connection if the path between the true stub connection and the mating interface is contained wholly within the connector housing1 *. Such connectors are termed housing-only connect
46、ors. Figure 1 shows examples of connectors, bus-paths, stubs, and stub connections in a single bus segment. 1 *This condition is common for connectors that are directly attached to flat ribbon cable. The true stub connection is the point where the wire of the ribbon cable meets the insulation displa
47、cement part of the connector contact and is not easily physically accessible. The stub contained within the connector housing is very short and very little error is introduced by considering the mating interface as the true stub connection. Page 13 STD.ANS1 TR-23-ENGL 3778 m 0724350 0553220 T3b I EP
48、I Rev 16 :c” DEVICE ATTACHED iz.-. DIRECTLY TO . ComEcmnl * * lrmn4mI)LB PATHGQ.IE - EXTENDING DEVICE NOT BEYOND BUS PATH Id := DIRECTLY ;o i I z :u :U :nE ATTACHED TO BUS PATH i-: DEVICE II ENCLOSI 8 : CONNECTOR MATING INTERFACE :I :i TERMINATOR U AN JRE :i :i -I T: ENABLED BUS SEGMENT TERMINATOR E
49、: END OF STUB - OFTEN ON A CHIP PAD * : TYPICALLY HOUSING-ONLY - BUS PATH: THE PATH BETWEEN THE TERMINATORS STUB: ANY NON-BUS PATH Figure 1 - Single segment physical architecture and terminology examples 5.2 SCSI domain related terminology and concepts SCSI domain: A SCSI domain is a logical bus with at least one bus segment, at least one initiator, and at least one target. Domains with multiple bus segments are enabled through the use of bus expanders. Domains consist of the set of SCSI devices that are addressable from an initiator or target. Wide domains a
