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

Transcription

10 April 2013
V01.00 Rev. A
10 April 2013
V01.00 Rev. A
MIL-STD-1760E Aircraft/Store Electrical Interconnection System, a Department of
Defense Interface Standard, was developed to reduce the proliferation of interfaces
between aircraft and their stores, and instead promote interoperability between
weapons 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.
Table of Contents
....................................................................................................1
Section 1 INTRODUCTION
....................................................................................................2
Section 2 MAKING SENSE
OF THE MYRIAD OF STANDARDS
....................................................................................................4
Section 3 HS1760 OVERVIEW
....................................................................................................5
Section 4 FIBRE CHANNEL
OVERVIEW
4.1 Deterministic
....................................................................................................................
5
Flow Control
4.2 Fibre Channel
....................................................................................................................
6
Exchange Management
....................................................................................................7
Section 5 FC-AE-1553 OVERVIEW
5.1 Mass Data....................................................................................................................
9
Transfer
5.2 From the....................................................................................................................
10
Platform to the Store
5.3 From the....................................................................................................................
11
Store to the Platform
Section 6 ADDITIONAL....................................................................................................13
AS5653 PROFILING
Section 7 ABOUT AIT
....................................................................................................14
MIL STD-1760E, HS1760, & FC-AE-1553 Protocol Tutorial
II
1
INTRODUCTION
MIL-STD-1760E Aircraft/Store Electrical Interconnection System, a Department of Defense
Interface Standard, was published 24 October 2007. MIL-STD-1760 was developed to
reduce the proliferation of interfaces between aircraft and their stores, (bombs, missiles,
countermeasures, and miscellaneous sensors), and instead promote interoperability between
weapons and aircraft platforms. It accomplished this by defining a standardized electrical
interface and connector that included both a digital and analog databus, a standardized
message protocol (MIL-STD-1553), power requirements, and discrete signals that would
serve as a standardized interface between the stores and the computer based stores
management systems. MIL-STD-1760 also defined the architectures allowed including
network topologies that resulted in the definition of various control and wiring harness points
like Carriage Store Interface (CSI), Aircraft Station Interface (ASI), Carriage Store Station
Interface (CSSI) and Mission Store Interface (MSI).
The end goal was to allow any given weapon to be easily hosted on many different aircraft
platforms 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 High
Bandwidth 2 and High Bandwidth 4 pins in the MIL-STD-1760 connector for Up Fibre
Channel and Down Fibre Channel respectively. This high-speed digital databus defined in the
SAE standard AS5653B has been given the popular name HS1760 (High-Speed 1760). The
purpose of this tutorial is to inform you of 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.
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2
MAKING SENSE OF THE MYRIAD OF STANDARDS
Figure 1: Relationship of INCITS Fibre Channel Standards and SAE Standards With
MIL-STD-1760E
Figure 1 above illustrates the various standards and their relationships to each other. Note that
the INCITS standards depicted are not the complete family of Fibre Channel standards. The
standards pictured are those that are important and relevant to a complete understanding of
what 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 standards
depicted in Figure 1. The three weapon interface standards represented by the SAE Aircraft
Store Interfaces block on Figure 1, especially AS5653B, are directly referenced by and
incorporated into MIL-STD-1760E. Then, as illustrated in Figure 1, the three weapon
interfaces 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 the
three 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 the
interface to Micro Munitions. AS5653B defines HS1760, the High-Speed Digital Data Bus
for MIL-STD-1760E. The motivation for separate standards for Miniature and Micro
Munitions lies in the weapons trend toward smaller smarter weapons associated with higheffectiveness and low collateral damage. For instance, Micro Munitions are envisioned to be
between 5 and 50 pounds in weight. In order to reduce the connector size for Micro
Munitions the pin count was reduced to 7 by multiplexing power over the Fibre Channel data
link.
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Table 1: Comparison of SAE Store Interfaces
Feature
Fibre Channel 1.0625 Gigabaud Serial Line Rate
AS5725
AS5726
AS5653B
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
Alternate Physical Network MIL-STD-1553B
Alternate Physical Network Extended Bit Rate 1553 (EBR1553 or SAE AS5652)
X
X
X
* For these Standards, Fibre Channel is the Class 1 option; the other interfaces are the
required primary interfaces
Table 1 above shows a brief comparison of these three standards in terms of their digital data
busses. The two common components of all modern digital data bus interfaces to smart
weapons is the use of Fibre Channel as the foundational standard operating at 1.0625
gigabaud and the use of FC-AE-1553 as the upper level protocol. Miniature Munitions
developed to the AS5725 standard may have two digital databus interfaces, one of which is
Fibre Channel the other is EBR-1553. Micro Munitions developed to the AS5726 standard
defines only Fibre Channel as its digital databus. Once again, as illustrated in Figure 1, all
three of these SAE standards rely upon the same family of Fibre Channel standards on the
right side of the bracket. Any difference between the three as far as the Fibre Channel
implementation goes is in the physical level.
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HS1760 OVERVIEW
HS1760 is the name given to the high-speed databus detailed in SAE AS5653B, designed for
and incorporated into MIL STD-1760E. The databus is essentially a profile of Fibre Channel
and FC-AE-1553, both of which are standards produced in the NCITS T11 committee
serving the commercial digital storage area network market.
The initial impetus behind HS1760 came as a request from the U.S. Navy seeking a highspeed weapons bus that would meet the needs of next generation of smart weapons that
would require more than a low-latency command & control databus. Initially, HS1760 was
seen as only running in parallel with MIL-STD-1553B in MIL-STD-1760E systems. In those
envisioned systems the venerable MIL-STD-1553B bus was assigned its traditional role as
the carrier of low-latency command and control messages. HS1760 Fibre Channel was seen
as handling the higher-bandwidth applications of file transfers, video image transfers, terrain
maps, and other high-bandwidth applications like sensors. With the introduction of the Micro
Munition standard (AS5726) there would be only one means of communication to the
weapon, HS1760 Fibre Channel. This means that the HS1760 databus must be able to
simultaneously handle mixed-mode data traffic. It must be able to handle the higherbandwidth traffic requirements envisioned for the newer smarter class of weapons including
mass memory transfers of initialization files while simultaneously guaranteeing the low-latency
command & control traffic historically handled by MIL-STD-1553B.
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4
FIBRE CHANNEL OVERVIEW
Fibre Channel is the product of INCITS (International Committee for Information Technology
Standards). INCITS operates under rules approved by the American Standards Institute
(ANSI) developing Information and Communication Technologies (ICT) encompassing
storage, processing, transfer, display, management, organization, and retrieval of information.
The Fibre Channel family of standards was developed primarily for the storage market place
and in fact Fibre Channel has been a highly successful data storage network since 1988
running billions of dollars in gross sales every year.
However, within the Fibre Channel working group there was a subgroup called the Avionics
Environment group that met and adapted Fibre Channel for the avionics community. As a
result Fibre Channel is the primary avionics bus on all the latest aircraft fighter programs in the
U.S. arsenal including the F-35, F-18E/F, and F-16 Block 50+. Fibre Channel has also been
used on some major avionics upgrade and enhancement programs including B-2 EHF, C130, and others. And finally, the focus for this paper, Fibre Channel was chosen for the highspeed weapons bus in AS5653B.
One question that often arises is, “Why wasn’t Ethernet used in all the above mentioned
industry solutions instead of Fibre Channel? After all, Fibre Channel and Gigabit Ethernet
share a common physical layer 8b/10b encoding, howbeit at a slightly different clock rate, so
why Fibre Channel?” There are two fundamental reasons why Fibre Channel is a good
choice. First, Fibre Channel is fundamentally more deterministic than Ethernet at the physical
level because of a credit based flow control mechanism that prevents any Fibre Channel port
from sending a frame if there is not a buffer available to receive that frame at the other end of
the link. Secondly, Fibre Channel defines all the levels of protocol up to the application. These
levels are summed up in the Fibre Channel Exchange Management that controls how two end
devices coordinate and control the flow of information between them. Fibre Channel
Exchange 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 of
avionics systems by reducing the scheduling burden placed upon the systems designer in that
data collisions do not have to be avoided by design. The deterministic flow control ensures
that competing users of critical shared buffer and transceiver resources are scheduled by the
system automatically. Combine that with the use of priorities and the systems designer has a
tool that enables him to construct a 'Plug & Play' system that works the way he wants it to
with low-latency messages getting first crack at critical shared data-link resources like
transceivers.
HS1760 (AS5653B) profiled this standard Fibre Channel behavior by doubling it so that
there would be two independent channels at each end of a Fibre Channel link. One channel
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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 traffic
associated with file transfers, video image transfers, and any other multi-frame Sequence that
would need to be sent. This prevents a high-bandwidth application from clogging the buffers
and thereby preventing a low-latency message from being forwarded on a link. Each channel
has its own buffers, the only resources being shared are the transceivers and wires that
comprise 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 to
communicate. Every upper level protocol has its own Exchange Manager. For instance, the
Exchange 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 FCP
which is a SCSI-3 Exchange Manager for the I/O data storage industry. The Exchange
Manager spans several levels of protocol including insight to the Upper Level Protocol level
down to the Fibre Channel FC-2 level which covers the bulk of Exchange Management. Its
efficiency is based both in its hardware oriented implementation as well as to its robust traffic
management capability.
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5
FC-AE-1553 OVERVIEW
FC-AE-1553 was chosen by the SAE AS5653B group as the upper level protocol of choice
for MIL-STD-1760E for two reasons. First, it offered the advantage of allowing the reuse of
legacy software written to MIL-STD-1553B. That means there is a direct mapping of the
command set that applications written for MIL-STD-1553B used to the command set for
FC-AE-1553. Secondly, FC-AE-1553 has the similar benefit of determinism offered by
MIL-STD-1553B in that there is a single entity, Controller, which initiates all I/O activity on
the 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, the
Network Terminal and the FC-AE switch. Table 5 lists some terminology equivalents
between MIL-STD-1553B and FC-AE-1553.
The basic FC-AE-1553 Exchanges are the NC to NT transfer, the NT to NC transfer and
the NT to NT transfer. Each Exchange is originated by the Network Controller and may be
viewed in the three figures below.
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Figure 5-I: NC to NT Transfer
Figure 5-II: NT to NC Transfer
Figure 5-III: NT to NT Transfer
8
For command & control traffic a Fibre Channel Sequence will be comprised of a single Fibre
Channel Frame that allows for 2048 bytes of user defined-data being included with the
command or status headers. If there is more than 2048 bytes of data to be transferred then it
falls 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 messages
types:
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 Transfer
to 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 the
actual file structure defined in MIL-STD-1760E enabling a backward compatibility to older
mass data transfer files. Each selected file (Sf) to be transferred using the FC-MDT Protocol
shall be divided into 1 to 255 consecutive records (Nr) with each record divided into 1 to
255 consecutive blocks (Nb). Each block contains 60 bytes with the first two bytes holding
the record/block number and the remaining 58 bytes used for file data. All records within a
specific file shall contain the same number of blocks. Unused words or bytes in each record
shall 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 be
sent using one FC-AE-1553 transfer using Burst Size Request. The purpose of the “Burst
Size Request” option is to allow the receiving port to control the pace and flow of data it is
receiving so that its receiving buffers are not overrun. Of course, Fibre Channel buffer-tobuffer credit based flow control mentioned earlier will prevent a frame from being sent on a
physical link for that priority-channel when there is not a physical link buffer for that priority-
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channel to receive it. But, after receiving frames into physical link buffers, they need to be
moved to a staging area where the entire transfer or Fibre Channel Sequence is being
assembled before presentation to the application program. The size of the staging area buffers
is what is being paced with the Burst Size Request option. For instance, the Mass Data
Transfer file structure blocks are 60 bytes and a single record contains 255 blocks. So every
record contains 15,300 bytes. Perhaps the staging area buffer would handle one record at a
time. As the staging buffer is filled, it is written to working memory or a storage device like a
disk drive or tape drive. The time it takes the receiving device to make that transfer within
itself is the time that it cannot handle any more data being received. This is also the amount of
time the receiving port will wait before it issues the status message back to the sending device
with the Burst Size Request bit enabled. A status message with the Burst Size Request bit set
is the trigger for the sending device to transmit the next Mass Data Transfer Record
embedded 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 Size
Request. The diagram of Figure 5 illustrates a FC-MDT transfer from the platform (NC) to
the store (NT). Every illustrated Fibre Channel Sequence represents a Mass Data Transfer
Record. Between the first and last Data Sequence is a cycle of Status Sequences and Data
Sequences flowing in opposite directions.
Figure 5.2: NC to NT Transfer with Burst Size Request
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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 receiving
NT being the NC using Burst Size Request. All Fibre Channel Frames shall be packed full
with the possible exception of the last one in the Sequence.
Figure 5.3: NT to NT Transfer with the NC being the Receiving NT
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6
ADDITIONAL AS5653 PROFILING
In addition to what has been covered, AS5653B also profiles several other miscellaneous
features including:
FHCP, Frame Header Control Protocol, is defined in FC-AV as the upper level
protocol for video or image transfers. This protocol is a very efficient transport
protocol developed especially for Fibre Channel and that takes advantage of the
Fibre Channel Header structure. Video, video with audio, and still images may all be
sent 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 those
specific to FC-AE-1553.
A select set of Extended Link Services, or ELS. These link services include SCR and
RSCN 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 be
deployed. Also included are a set of ELS routines to allow the NC to read and write
to the Principal switch the Fast Fabric Initialization Domain Topology Map. This gives
a standardized way for the system to initialize the weapon or stores load as well as a
standardized way to communicate dynamically changes to the store load status.
Switch features including the ability to broadcast messages, but not multicast, the
support of two independent priority channels, and NC/NT subsystems initialization
and login functions relative to the switch.
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ABOUT AIT
Avionics Interface Technologies
AIT offers a full range of solutions to the HS1760 user and developer. Products include
HS1760 IP CORE, embedded end-systems, test systems, and verification and validation
equipment as well as HS1760 switches. Our HS1760 products are complete hardware and
software 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 HS1760
products will simulate a Network Controller (NC) as well as Network Terminal (NT). The
products 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.
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MIL-STD-1760E, HS1760, AND FC-AE-1553

Transcription

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