mil-std-1760e, hs1760, and fc-ae-1553 · mil-std-1760e, hs1760, and fc-ae-1553 ... network...

MIL-STD-1760E, HS1760, AND FC-AE-1553

GARY WARDEN

10 April 2013

GARY WARDEN

10 April 2013

MIL-STD-1760E, HS1760, AND FC-AE-1553

MIL-STD-1760E Aircraft/Store Electrical Interconnection System, a Department ofDefense Interface Standard, was developed to reduce the proliferation of interfaces

between aircraft and their stores, and instead promote interoperability betweenweapons and aircraft platforms. The purpose of this tutorial is to outline HS1760,bring sense to the myriad of standards that define the new protocols, and point out

some major performance and feature enhancements enabled by HS1760.

MIL STD-1760E, HS1760, & FC-AE-1553 Protocol Tutorial II

Table of Contents

Section 1 ....................................................................................................1INTRODUCTION

Section 2 ....................................................................................................2MAKING SENSE OF THE MYRIAD OF STANDARDS

Section 3 ....................................................................................................4HS1760 OVERVIEW

Section 4 ....................................................................................................5FIBRE CHANNEL OVERVIEW

.................................................................................................................... 54.1 Deterministic Flow Control

.................................................................................................................... 64.2 Fibre Channel Exchange Management

Section 5 ....................................................................................................7FC-AE-1553 OVERVIEW

.................................................................................................................... 95.1 Mass Data Transfer

.................................................................................................................... 105.2 From the Platform to the Store

.................................................................................................................... 115.3 From the Store to the Platform

Section 6 ....................................................................................................13ADDITIONAL AS5653 PROFILING

Section 7 ....................................................................................................14ABOUT AIT

MIL STD-1760E, HS1760, & FC-AE-1553 Protocol Tutorial1

1 INTRODUCTION

MIL-STD-1760E Aircraft/Store Electrical Interconnection System, a Department of DefenseInterface Standard, was published 24 October 2007. MIL-STD-1760 was developed toreduce the proliferation of interfaces between aircraft and their stores, (bombs, missiles,countermeasures, and miscellaneous sensors), and instead promote interoperability betweenweapons and aircraft platforms. It accomplished this by defining a standardized electricalinterface and connector that included both a digital and analog databus, a standardizedmessage protocol (MIL-STD-1553), power requirements, and discrete signals that wouldserve as a standardized interface between the stores and the computer based storesmanagement systems. MIL-STD-1760 also defined the architectures allowed includingnetwork topologies that resulted in the definition of various control and wiring harness pointslike Carriage Store Interface (CSI), Aircraft Station Interface (ASI), Carriage Store StationInterface (CSSI) and Mission Store Interface (MSI).

The end goal was to allow any given weapon to be easily hosted on many different aircraftplatforms and, vice versa, allow any given aircraft platform to host many different weapons.The major difference between MIL-STD-1760E and its predecessor MIL-STD-1760D(published in August of 2003) is the inclusion of a high speed digital databus utilizing the HighBandwidth 2 and High Bandwidth 4 pins in the MIL-STD-1760 connector for Up FibreChannel and Down Fibre Channel respectively. This high-speed digital databus defined in theSAE standard AS5653B has been given the popular name HS1760 (High-Speed 1760). Thepurpose of this tutorial is to inform you of HS1760, bring sense to the myriad of standardsthat define the new protocols, and point out some major performance and featureenhancements enabled by HS1760.

MIL STD-1760E, HS1760, & FC-AE-1553 Protocol Tutorial 2

2 MAKING SENSE OF THE MYRIAD OF STANDARDS

Figure 1: Relationship of INCITS Fibre Channel Standards and SAE Standards WithMIL-STD-1760E

Figure 1 above illustrates the various standards and their relationships to each other. Note thatthe INCITS standards depicted are not the complete family of Fibre Channel standards. Thestandards pictured are those that are important and relevant to a complete understanding ofwhat is implemented in MIL-STD-1760E’s high-speed digital databus (HS1760).

MIL-STD-1760E is the base weapons systems standard that invokes the other standardsdepicted in Figure 1. The three weapon interface standards represented by the SAE AircraftStore Interfaces block on Figure 1, especially AS5653B, are directly referenced by andincorporated into MIL-STD-1760E. Then, as illustrated in Figure 1, the three weaponinterfaces are reliant upon the Fibre Channel standards shown to the right of the bracket.Finally, the three SAE Validation Test Plans, which are works in progress still in committee,are testing Network Controllers, Network Terminals, and FC-AE Switches. These are thethree active components foundational to the SAE Aircraft Store Interfaces.

As illustrated in Figure 1 there are three SAE standards that define interfaces to stores(weapons). AS5725 defines the interface to Miniature Munitions. AS5726 defines theinterface to Micro Munitions. AS5653B defines HS1760, the High-Speed Digital Data Busfor MIL-STD-1760E. The motivation for separate standards for Miniature and MicroMunitions lies in the weapons trend toward smaller smarter weapons associated with high-effectiveness and low collateral damage. For instance, Micro Munitions are envisioned to bebetween 5 and 50 pounds in weight. In order to reduce the connector size for MicroMunitions the pin count was reduced to 7 by multiplexing power over the Fibre Channel datalink.


Table 1: Comparison of SAE Store Interfaces

Feature AS5725 AS5726 AS5653B

Fibre Channel 1.0625 Gigabaud Serial Line Rate X* X X*

Power Multiplexed Over Fibre Channel Data Lines X

75 Ohm Single Ended Coax Wires X

150 Ohm Differential Pair Wires X X

FC-AE-1553 Upper Level Protocol X X X

Alternate Physical Network MIL-STD-1553B X

Alternate Physical Network Extended Bit Rate 1553 (EBR-1553 or SAE AS5652)

X

* For these Standards, Fibre Channel is the Class 1 option; the other interfaces are therequired primary interfaces

Table 1 above shows a brief comparison of these three standards in terms of their digital databusses. The two common components of all modern digital data bus interfaces to smartweapons is the use of Fibre Channel as the foundational standard operating at 1.0625gigabaud and the use of FC-AE-1553 as the upper level protocol. Miniature Munitionsdeveloped to the AS5725 standard may have two digital databus interfaces, one of which isFibre Channel the other is EBR-1553. Micro Munitions developed to the AS5726 standarddefines only Fibre Channel as its digital databus. Once again, as illustrated in Figure 1, allthree of these SAE standards rely upon the same family of Fibre Channel standards on theright side of the bracket. Any difference between the three as far as the Fibre Channelimplementation goes is in the physical level.


3 HS1760 OVERVIEW

HS1760 is the name given to the high-speed databus detailed in SAE AS5653B, designed forand incorporated into MIL STD-1760E. The databus is essentially a profile of Fibre Channeland FC-AE-1553, both of which are standards produced in the NCITS T11 committeeserving the commercial digital storage area network market.

The initial impetus behind HS1760 came as a request from the U.S. Navy seeking a high-speed weapons bus that would meet the needs of next generation of smart weapons thatwould require more than a low-latency command & control databus. Initially, HS1760 wasseen as only running in parallel with MIL-STD-1553B in MIL-STD-1760E systems. In thoseenvisioned systems the venerable MIL-STD-1553B bus was assigned its traditional role asthe carrier of low-latency command and control messages. HS1760 Fibre Channel was seenas handling the higher-bandwidth applications of file transfers, video image transfers, terrainmaps, and other high-bandwidth applications like sensors. With the introduction of the MicroMunition standard (AS5726) there would be only one means of communication to theweapon, HS1760 Fibre Channel. This means that the HS1760 databus must be able tosimultaneously handle mixed-mode data traffic. It must be able to handle the higher-bandwidth traffic requirements envisioned for the newer smarter class of weapons includingmass memory transfers of initialization files while simultaneously guaranteeing the low-latencycommand & control traffic historically handled by MIL-STD-1553B.


4 FIBRE CHANNEL OVERVIEW

Fibre Channel is the product of INCITS (International Committee for Information TechnologyStandards). INCITS operates under rules approved by the American Standards Institute(ANSI) developing Information and Communication Technologies (ICT) encompassingstorage, processing, transfer, display, management, organization, and retrieval of information.The Fibre Channel family of standards was developed primarily for the storage market placeand in fact Fibre Channel has been a highly successful data storage network since 1988running billions of dollars in gross sales every year.

However, within the Fibre Channel working group there was a subgroup called the AvionicsEnvironment group that met and adapted Fibre Channel for the avionics community. As aresult Fibre Channel is the primary avionics bus on all the latest aircraft fighter programs in theU.S. arsenal including the F-35, F-18E/F, and F-16 Block 50+. Fibre Channel has also beenused on some major avionics upgrade and enhancement programs including B-2 EHF, C-130, and others. And finally, the focus for this paper, Fibre Channel was chosen for the high-speed weapons bus in AS5653B.

One question that often arises is, “Why wasn’t Ethernet used in all the above mentionedindustry solutions instead of Fibre Channel? After all, Fibre Channel and Gigabit Ethernetshare a common physical layer 8b/10b encoding, howbeit at a slightly different clock rate, sowhy Fibre Channel?” There are two fundamental reasons why Fibre Channel is a goodchoice. First, Fibre Channel is fundamentally more deterministic than Ethernet at the physicallevel because of a credit based flow control mechanism that prevents any Fibre Channel portfrom sending a frame if there is not a buffer available to receive that frame at the other end ofthe link. Secondly, Fibre Channel defines all the levels of protocol up to the application. Theselevels are summed up in the Fibre Channel Exchange Management that controls how two enddevices coordinate and control the flow of information between them. Fibre ChannelExchange Management is both more deterministic and efficient than the IP (Internet Protocol)stack often used in Ethernet applications.

4.1 Deterministic Flow Control

Fibre Channel’s deterministic flow control reduces the cost of the design and validation ofavionics systems by reducing the scheduling burden placed upon the systems designer in thatdata collisions do not have to be avoided by design. The deterministic flow control ensuresthat competing users of critical shared buffer and transceiver resources are scheduled by thesystem automatically. Combine that with the use of priorities and the systems designer has atool that enables him to construct a 'Plug & Play' system that works the way he wants it towith low-latency messages getting first crack at critical shared data-link resources liketransceivers.

HS1760 (AS5653B) profiled this standard Fibre Channel behavior by doubling it so thatthere would be two independent channels at each end of a Fibre Channel link. One channel


would be for the high-priority traffic generally associated with the low-latency command &control traffic and the other channel would be associated with the high-bandwidth trafficassociated with file transfers, video image transfers, and any other multi-frame Sequence thatwould need to be sent. This prevents a high-bandwidth application from clogging the buffersand thereby preventing a low-latency message from being forwarded on a link. Each channelhas its own buffers, the only resources being shared are the transceivers and wires thatcomprise the physical link.

4.2 Fibre Channel Exchange Management

Fibre Channel Exchange Management is core to the power and efficiency of Fibre Channel.Exchange Management serves as an operation manager between two end devices wishing tocommunicate. Every upper level protocol has its own Exchange Manager. For instance, theExchange Management for FC-AE-1553 is very different from an Internet Protocol (IP)Exchange Manager or an ASM (Anonymous Subscriber Messenger) Exchange Manager.The most widely distributed and used Exchange Manager in the Fibre Channel world is FCPwhich is a SCSI-3 Exchange Manager for the I/O data storage industry. The ExchangeManager spans several levels of protocol including insight to the Upper Level Protocol leveldown to the Fibre Channel FC-2 level which covers the bulk of Exchange Management. Itsefficiency is based both in its hardware oriented implementation as well as to its robust trafficmanagement capability.


5 FC-AE-1553 OVERVIEW

FC-AE-1553 was chosen by the SAE AS5653B group as the upper level protocol of choicefor MIL-STD-1760E for two reasons. First, it offered the advantage of allowing the reuse oflegacy software written to MIL-STD-1553B. That means there is a direct mapping of thecommand set that applications written for MIL-STD-1553B used to the command set forFC-AE-1553. Secondly, FC-AE-1553 has the similar benefit of determinism offered byMIL-STD-1553B in that there is a single entity, Controller, which initiates all I/O activity onthe network.

Table 5: Comparison of 1553 Active Components

MIL-STD-1553B FC-AE-1553

Bus Controller (BC) Network Controller (NC)

Remote Terminal (RT) Network Terminal (NT)

RT Address Network Terminal Address

RT Subaddress NT Subaddress (NT_SA)

MIL-STD-1553 Message FC-AE-1553 Exchange

Command Word Command Sequence

Status Word Status Sequence

There are three active components in a FC-AE-1553 network: the Network Controller, theNetwork Terminal and the FC-AE switch. Table 5 lists some terminology equivalentsbetween MIL-STD-1553B and FC-AE-1553.

The basic FC-AE-1553 Exchanges are the NC to NT transfer, the NT to NC transfer andthe NT to NT transfer. Each Exchange is originated by the Network Controller and may beviewed in the three figures below.


Figure 5-I: NC to NT Transfer

Figure 5-II: NT to NC Transfer

Figure 5-III: NT to NT Transfer


For command & control traffic a Fibre Channel Sequence will be comprised of a single FibreChannel Frame that allows for 2048 bytes of user defined-data being included with thecommand or status headers. If there is more than 2048 bytes of data to be transferred then itfalls into the realm of a Mass Data Transfer.

5.1 Mass Data Transfer

Mass Data Transfers as defined in MIL-STD-1760E are comprised of three data messagestypes:

1. The Transfer Control (TC)2. The Transfer Monitor (TM)3. The Transfer Data (TD)

Figures 5.1-II and 5.1-II below define a simple mapping of the historical Mass Data Transferto the Fibre Channel protocol using FC-AE-1553. This mapping may be called FC-MDT(Fibre Channel – Mass Data Transfer). In this mapping there are essentially no changes to theactual file structure defined in MIL-STD-1760E enabling a backward compatibility to oldermass data transfer files. Each selected file (Sf) to be transferred using the FC-MDT Protocolshall be divided into 1 to 255 consecutive records (Nr) with each record divided into 1 to255 consecutive blocks (Nb). Each block contains 60 bytes with the first two bytes holdingthe record/block number and the remaining 58 bytes used for file data. All records within aspecific file shall contain the same number of blocks. Unused words or bytes in each recordshall be zero-filled. The entire file shall be transferred as one Fibre Channel Sequence.

The entire file may be visualized as a single data structure in a buffer. The entire buffer will besent using one FC-AE-1553 transfer using Burst Size Request. The purpose of the “BurstSize Request” option is to allow the receiving port to control the pace and flow of data it isreceiving so that its receiving buffers are not overrun. Of course, Fibre Channel buffer-to-buffer credit based flow control mentioned earlier will prevent a frame from being sent on aphysical link for that priority-channel when there is not a physical link buffer for that priority-


channel to receive it. But, after receiving frames into physical link buffers, they need to bemoved to a staging area where the entire transfer or Fibre Channel Sequence is beingassembled before presentation to the application program. The size of the staging area buffersis what is being paced with the Burst Size Request option. For instance, the Mass DataTransfer file structure blocks are 60 bytes and a single record contains 255 blocks. So everyrecord contains 15,300 bytes. Perhaps the staging area buffer would handle one record at atime. As the staging buffer is filled, it is written to working memory or a storage device like adisk drive or tape drive. The time it takes the receiving device to make that transfer withinitself is the time that it cannot handle any more data being received. This is also the amount oftime the receiving port will wait before it issues the status message back to the sending devicewith the Burst Size Request bit enabled. A status message with the Burst Size Request bit setis the trigger for the sending device to transmit the next Mass Data Transfer Recordembedded within a Fibre Channel Sequence.

5.2 From the Platform to the Store

From the platform to the store the transfer will be a NC to NT transfer using Burst SizeRequest. The diagram of Figure 5 illustrates a FC-MDT transfer from the platform (NC) tothe store (NT). Every illustrated Fibre Channel Sequence represents a Mass Data TransferRecord. Between the first and last Data Sequence is a cycle of Status Sequences and DataSequences flowing in opposite directions.

Figure 5.2: NC to NT Transfer with Burst Size Request


5.3 From the Store to the Platform

In the store to platform direction the transfer shall be a NT to NT transfer with the receivingNT being the NC using Burst Size Request. All Fibre Channel Frames shall be packed fullwith the possible exception of the last one in the Sequence.

Figure 5.3: NT to NT Transfer with the NC being the Receiving NT


6 ADDITIONAL AS5653 PROFILING

In addition to what has been covered, AS5653B also profiles several other miscellaneousfeatures including:

FHCP, Frame Header Control Protocol, is defined in FC-AV as the upper levelprotocol for video or image transfers. This protocol is a very efficient transportprotocol developed especially for Fibre Channel and that takes advantage of theFibre Channel Header structure. Video, video with audio, and still images may all besent with a standardized containerization protocol defined in FC-AV.A special set of Fibre Channel timeout values unique for MIL-STD-1760E systems.These timeout values are ones normal to standard Fibre Channel as well as thosespecific to FC-AE-1553.A select set of Extended Link Services, or ELS. These link services include SCR andRSCN which allow the NC to become aware of link state changes on the switches.These are useful to detect when a store has powered up, powered down, or bedeployed. Also included are a set of ELS routines to allow the NC to read and writeto the Principal switch the Fast Fabric Initialization Domain Topology Map. This givesa standardized way for the system to initialize the weapon or stores load as well as astandardized way to communicate dynamically changes to the store load status. Switch features including the ability to broadcast messages, but not multicast, thesupport of two independent priority channels, and NC/NT subsystems initializationand login functions relative to the switch.


7 ABOUT AIT

Avionics Interface Technologies

AIT offers a full range of solutions to the HS1760 user and developer. Products includeHS1760 IP CORE, embedded end-systems, test systems, and verification and validationequipment as well as HS1760 switches. Our HS1760 products are complete hardware andsoftware solutions.

The HS1760 products supports the standard FC-AE-1553 frame formats for command,control, and other data communications as profiled in the SAE AS5653. The HS1760products will simulate a Network Controller (NC) as well as Network Terminal (NT). Theproducts can also be used in SAE AS5725, Miniature Munitions Store Interface (MMSI)Rev. D as well as SAE AS5726 Interface for Micro Munitions (IMM) applications.

mil-std-1760e, hs1760, and fc-ae-1553 · mil-std-1760e, hs1760, and fc-ae-1553 ... network...

Documents