Frequently Asked Questions and Answers

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What are the key advantages of EBR-1553 over other high-speed communication standards?

EBR-1553 incorporates the advantages of legacy-1553, and accelerates the communication by 10.

It is important to identify that 1553 and CAN Bus are targeted for physical control of systems, and not for voice data or video communication.

Control communication is required to provide real-time operation, as opposed to data communication which is required to transfer large amounts of data from point A to B.

For that reason, control-communication standards need to have very compact messaging which repeats itself 50 to 100 times per second. 

As of today, 2024, for control-buses such as 1553, CAN Bus and ARINC429, EBR-1553 is the fastest protocol available for new designs.

EBR-1553 is easily scalable. The RS-485 transceivers support rates of more than 50M bps, and the solid state digital chip can be fed with higher frequencies. The required effort to support 20 Mbps and 40 Mbps EBR-1553 variants is not high, making it future proof.  

What software and testing tools are available for developers working with EBR-1553?

There are more than a few vendors that supply EBR-1553 test tools. These tools complement the developed node.

Some vendors have inherent limitations in the wire lengths due to poor signaling in their EBR-1553 encoder – decoder. A good EBR-1553 tester should support 40 meters (120 feet)  of cables. 

How does EBR-1553 handle noise immunity and data integrity at higher data rates?

The RS-485 physical layer transceivers are built for very high frequency and easily support 10 M-bps. If the OEM assures the wires are twisted correctly, and are of the exact same length, noise immunity is maintained. 

Since the signal is ground referenced, a ground wire is needed between the BC and each RT.

What are the limitations or challenges associated with the adoption of EBR-1553?

As in MIL-STD-1760, EBR-1553 does not support RT-to-RT transfers.

EBR-1553 does not have redundancy, only bus A. However, a munition can support two RTs, and by that provide redundancy. 

RS-485 transceivers are not ground floating like legacy-1553 is, and thus less robust.

There is no formal RT-Validation testing in EBR-1553. This reduces the interoperability between vendors. As a result, there are two known variants of the EBR-1553 signal shape, one for Lockheed and another for Boeing. A decoder that supports both is required.  

Transformers in legacy-1553 systems are better immune to lightning than ground referenced physical layers.

What are the HUB modes available for EBR-1553?

There are three HUB modes in EBR-1553:

SPEC mode – RTs have an RT address, 0 to 30, and each has its port on the hub.

SWITCH mode – For a four RT system, the first RT will support RT numbers 0, 4, 8… The second supports 1, 5, 9… and so on.

LINK mode – all RTs are address 0 (!) and the BC sends all messages to RT0, but the RT number addressed depends on its port number in the hub.

From all EBR-1553 HUB modes, Link mode is the only one actually used.

Link mode implementation requires additional modifications to the legacy-1553 digital chip. There are very few companies that implement EBR-1553 BC HUB in Link mode in the digital chip, others provide work-arounds.

What are the typical configurations available for EBR-1553, such as Bus Controller (BC), Remote Terminal (RT), and Bus Monitor?

EBR-1553 uses the same digital part, running 10 times faster. That implies that it supports the very same features as the legacy-1553 chip, including BC, RT, MT, RT-MON, and Multiple RTs.

How does EBR-1553 improve communication for advanced systems like smart munitions?

EBR-1553 multiplies the bit rate by 10, allowing more data transfer such as image of target transferred to smart munition after take-off.

What hardware is required to implement EBR-1553, and how does it utilize RS-485 transceivers?

A typical EBR-1553 implementation is composed of a digital part that can be implemented in an FPGA or ASIC, and RS-485 transceiver for the physical layer..

RS-485 transceivers are single ended as opposed to legacy-1553 transceivers which are double ended. This implies that a new decoder encoder is required in the digital portion of the EBR-1553 compared with the legacy-1553 implementation. 

Can EBR-1553 be integrated into existing MIL-STD-1553 systems without extensive rewiring?

No, rewiring is required. EBR-1553 requires different wires with typical impedance of 120 Ohms, as opposed to legacy 1553 wiring that is 78-Ohms.

For new systems, such as drones, and cruise missiles, EBR-1553 is highly recommended.

How does the star topology of EBR-1553 enhance data transmission compared to the bus topology of MIL-STD-1553?

The bit rate is 10M-bps rather than 1M-bps in legacy MIL-STD-1553, speeds up the transfer by a factor of 10.

Using a network topology of a star between BC and Remote Terminals traditionally uses only one of the RT links, but in theory may support multiple BCs communicating with multiple RTs in parallel on all links concurrently.

For example, legacy 1553 can transfer 1 M-bps to, say, four RTs. Maximum rate would be 250 Kbps for each.

EBR-1553 can transfer 10 Mbps to those four RTs at 2.5M bps each.

4 x EBR-1553 BCs can transfer 40 Mbps in parallel, each RT is getting 10 Mbps. 

So potentially, EBR-1553 with star topology can deliver 40 x faster.

With tomorrow’s munitions, these rates are highly required.

What are the primary applications and use cases for EBR-1553?

The MMSI (Miniature Munitions Stores Interface) or EBR1553 data bus is a relatively simple  network protocol used to share data between avionics subsystems. EBR-1553 is deployed on weapon systems, including Small Diameter Bomb (SDB). Sital’s EBR-1553 components provide DDC’s Enhanced Mini-ACE register/memory architecture; BC, RT, and Monitor operation. It also includes a hub that can be instantiated to provide any number of ports up to and including 31 nodes.

What is EBR-1553 and how does it differ from MIL-STD-1553?

EBR-1553 is a 10Mbps bit rate protocol which utilized the robust Mil-Std-1553 protocol over RS-485 transceivers in a hub-based point-to-point connection.

What is the cost of MIL-STD-1553B?

Depending on if you are buying a component $400-$1800. IP Cores range from $15,000-$25,000. A software driver for MIL-STD-1553 usually around $22,000

What are the advantages of DFDs (Data Flow Documents)

Data Flow Documents (DFDs) are important because they help you visualize how data moves through your system, spot inefficiencies, and find opportunities to improve overall functionality.

What are the advantages of a linear bus?

MIL-STD-1553 operates over a multi-drop bus, which can sometimes be considered a linear topology. Here are some advantages of this bus configuration:

  1. It is relatively easy to set up and extend.
  2. The required cable length is minimal compared to other network topologies.
  3. It is cost-effective, making it a budget-friendly option.
  4. Multi-drop bus configurations are often used in small networks, especially in military and aerospace applications.

What are the advantages and disadvantages of the Modbus protocol?

The Modbus protocol is an important protocol in the industrial IoT field. It boasts advantages such as simplicity, scalability, and wide applicability. However, its relatively slow speed and insufficient security need to be considered in practical applications.

What is the impedance of MIL-STD-1553?

MIL-STD-1553 data bus specification requires a shielded twisted pair cable with an impedance of 70–85 ohms at 1 MHz. The industry has standardized on a Twinax cable with a nominal characteristic impedance of 78 ohms, which is near the center of the specification range.

What is the frequency of MIL-STD-1553?

The MIL-STD-1553 standard uses Manchester II Bi-Phase encoding of all bits. The data rate is 1 MHz, implemented by a Manchester symbol rate of 2 Mbd.

What is the voltage of MIL-STD-1553?

For transmission, MIL-STD-1553 mandates a range of stub voltages between 6.0 and 9.0 volts peak-to-peak for direct-coupled stubs. For transformer-coupled stubs, the required voltage range is between 18.0 and 27.0 volts peak-to-peak.

MIL-STD-1553 also specifies receiver threshold voltages between 0.28 and 1.2 volts peak-to-peak for direct-coupled stubs and between 0.20 and 0.86 volts peak-to-peak for transformer-coupled stubs. In addition, terminal input impedance must be a minimum of 2,000 ohms for directed-coupled stubs and 1,000 ohms for transformer-coupled stubs.

What are the applications of MIL-STD-1553B?

Today, MIL-STD-1553’s application has gone further than the traditional domain of US Navy and Air Force aircraft. It include applications utilized in combat vehicles, missiles, ships, launch vehicles, satellites and the International Space Station Program. It’s also being used in some commercial aircraft applications.

What type of cable does MIL-STD-1553 use?

MIL-STD-1553 uses twinax cables with a typical characteristic impedance of 78 ohms. This impedance is close to the center of the specification range of 70 to 85 ohms. The cables are often used with concentric twinax connectors, which have a center contact and an intermediate cylindrical inner shield contact.

Is MIL-STD-1553 still used?

MIL-STD-1553 will be around for a long time. This is due to its large installed base and the caution military programs exercise in using alternatives. The long history of the MIL-STD-1553, along with its high reliability from a reliable physical layer, familiar command/response protocol, and redundancy makes it a trusted choice.

How does MIL-STD-1553 communication work?

MIL-STD-1553 communication works by designating a single active Bus controller to manage data flow to, from, and between multiple remote terminals. The bus operates in a time-division multiplexed manner, where data is transmitted in messages consisting of “words”.

All words begin with a 3 µs “Sync” field and include a fixed number of data bits (16) and a single parity bit for error-checking each word. There are three types of words: Command words, transmitted by Bus controllers (BCs); Status words, transmitted by remote terminals (RTs); and Data words, transmitted by either BCs or RTs.

Messages are made up of a defined series of words. Different message formats allow the bus controller (BC) to send data to remote terminals (RTs), RTs to send data to the BC, or one RT to send data to another RT.

Broadcast messages let the BC or an RT send data to all RTs on the bus. Meanwhile, “mode code” messages manage bus functions and contain either no data words or just one data word.

MIL-STD-1553 Tutorial and Reference:

Here are some details about how MIL-STD-1553 communication works:

  • Time Division

Only one computer terminal can transmit at any given time, while the other computers listen and receive. This is different from full-duplex systems like Ethernet and RS-232, which allow simultaneous transmit and receive on different wires.

  • Bus Controller

The bus controller is the only device that can transmit command words, which initiate all messages. Command words contain the remote terminal’s address, direction of message transmission, subaddress, and word count.

  • Data Words

The bus controller can send 1 to 32 data words when using BC-to-RT transfers or broadcast data messages. For broadcast messages, all remote terminals accept the data, but no terminals respond with Status words.

  • Remote and Control Devices

The Bus controller, Remote terminals, and Monitor devices are interconnected over two separate buses. Normal operation involves only the primary bus, with the secondary bus available as a redundant backup if the primary bus fails.

  • Message Scheduling

With MIL-STD-1553, most messaging is synchronous; i.e., based on periodic scheduling. In some systems, high-priority aperiodic messages are inserted into gaps between scheduled messages. Whereas, low priority aperiodic messages are inserted at the end of a minor frame.

What is Enhanced Bit Rate 1553?

Known as EBR-1553, this is a communication standard derived from MIL-STD-1553 but engineered for a higher data rate of 10 Mb/s. Instead of operating over a multi-drop bus, it calls for the use of a hub (star) topology and a point-to-point physical layer based on RS-485 transceivers.

What is a MIL-STD-1553 channel?

For MIL-STD-1553, the definition of the word “channel” depends on the context. Sometimes it refers to a dual redundant data bus. Other times, it refers to the fact that a dual redundant bus includes two “channels”. These two channels are sometimes referred to as “Channel A” and Channel B”.

In other contexts, they’re referred to as the “primary channel” and the “secondary channel” or “backup channel”. In either context, the requirements for a MIL-STD-1553 channel include the electrical, mechanical, and operating characteristics of a serial data communication bus defined by the 1553 channel.

What is the purpose of the MIL-STD-1553 bus coupler?

The purpose of a MIL-STD-1553 bus coupler is to maintain signal impedance levels and reduce reflections. Couplers are connected between the MIL-STD-1553 bus and 1553 stubs. Stubs can be up to 20 feet long and connect to Bus controllers, Remote terminals, and Monitors.

They include transformers with a fixed turns stepped-down ratio of 1.4 to 1.0 from the bus to the stub. Additionally, fault-isolation resistors with values of 0.75*Z0 are placed on the bus side of the transformers. These resistors are included to protect the bus from short circuit faults on stubs or in terminals. This prevents a short circuit on a single stub or terminal from shorting out the main bus, which could cause the entire bus to fail.

Couplers also provide enhanced DC isolation, common mode rejection, and lightning protection for connected terminals. This is in addition to the protection offered by the terminals’ internal isolation transformers.

What is the difference between MIL-STD-1553 and ARINC-429?

MIL-STD-1553 and ARINC-429 are both data bus standards that are widely used in avionics systems. ARINC-429 employs a point-to-point(s) physical layer topology and can therefore operate in a single-cast or multicast mode.

ARINC-429 is primarily used in commercial aircraft but is also used in helicopters and other military applications. MIL-STD-1553 operates over a dual redundant multi-drop bus and is ideal for real-time mission-critical applications. It supports single-cast or multicast messages.

Some applications use multi-I/O boards that include both MIL-STD-1553 and ARINC-429 interfaces. Such boards can also include interfaces for other military databus protocols, including EBR-1553 and CAN bus/ARINC-825. Although CANbus is used primarily in commercial automotive applications, it’s also used in military ground vehicles. It is also utilized with heavy industrial and agricultural vehicles.

Is MIL-STD-1553 Ethernet?

No, MIL-STD-1553 is not Ethernet. However, it can be bridged with Ethernet in some systems. MIL-STD-1553 is a military standard for serial data buses that has been used for over 40 years.

While MIL-STD-1553 and Ethernet are different technologies, hybrid systems can combine them by using Ethernet’s OSI model to create two communication channels. This setup can enhance error detection and improve reliability.

What is the difference between MIL-STD-1553 and RS-485?

Like MIL-STD-1553, RS-485 is based on the use of differential signaling. However, in many respects, RS-485 is a less robust standard than 1553. For example, RS-485’s minimum bus voltage is 1.5 volts peak (3.0 volts peak-to-peak), which is half of the MIL- STD-1553 minimum bus voltage of 6.0 volts peak-to-peak. In addition, unlike RS-485, MIL-STD-1553 calls for balanced signaling and transformer isolation.

How fast is the MIL-STD-1553 bus?

MIL-STD-1553 is a serial multiplex data bus with a transmission speed of 1 megabit per second (Mbps). This speed is equivalent to 1 bit per microsecond. The bus is made up of a shielded twisted-wire pair with an impedance of 70 to 85 ohms at 1 MHz.

Transmitter and receiver devices connect to the bus through isolation transformers. In the most commonly used configuration referred to as transformer coupling, there are also transformers built into the couplers. These couplers provide a physical connection to the bus and stubs.

What are the advantages of MIL-STD-1553?

MIL-STD-1553 is reliable due to its physical layer, which offers high noise immunity and reliable data transmission over long distances. Its command/response protocol provides deterministic communication for precise control and validation testing.

Additionally, dual redundancy provides an extra layer of reliability. These features make it a highly dependable data bus for military and aerospace applications.

What is MIL-STD-1553 and how does it work?

MIL-STD-1553 is a message transmission-based bus that defines ten different message types. Most message formats consist of Command words, Status words, and Data words. These words enable communication between system elements.

The bus controller initiates and controls all bus communications, while remote terminal devices attached to the bus respond to the controller’s commands.

The standard defines specifications for terminal devices.

Here are some terms related to MIL-STD-1553:

  • Bus Monitor

CA bus monitor can be configured to receive words from either one or both dual redundant 1553 buses. Bus monitors are passive listeners on 1553 buses. They receive and store words received from the bus but never transmit.

  • Command Word

A type of word transmitted by a bus controller. Its 16 bits include the remote terminal’s 5-bit address, 5-bit subaddress, and a 5-bit word count. There is also a bit to indicate if the remote terminal receiving the Command word will either receive or transmit data.

  • Data Word

All 1553 data words are 16 bits long. Data words may be transmitted by either the BC or an RT. Other than designating the first bit transmitted as the MSB, MIL-STD-1553 does not define the bit definitions and formats of data words. These are typically defined by system-level ICDs (Interface Control Documents).

  • Status Word

Status words are transmitted by Remote Terminals. The first five bits provide the RT’s address and provide acknowledgement to the bus controller. Other status word bits convey the status of the RT or the connected sub-system.

  • Cards

There are multiple types of cards: multi-function, single-function, and dual-function. Multi-function cards can support the three functions simultaneously. This includes managing a bus and emulating one or more RTs at the same time.

Single-function cards can also support the three functions, but not simultaneously. Dual-function cards can support BC + Monitor or RT + Monitor modes simultaneously.

Where is MIL-STD-1553 used?

MIL-STD-1553 is a communication standard used in military systems for reliable data transfer. While bridging between TCP/IP or UDP/IP and MIL-STD-1553 is possible through proprietary methods, TCP/IP and UDP/IP themselves are not natively used with MIL-STD-1553.

The MIL-STD-1553 standard is used for systems integration in flight controls, weapon systems, military avionics, and spacecraft. The International Space Station utilizes it for onboard data handling. It is also commonly found in fighter jets, attack aircraft, cargo planes, helicopters, and some military ground vehicles.

What is the purpose and specification of MIL-STD-1553?

MIL-STD-1553 is a standard that was established as a U.S. Air Force standard in 1973 and first used on the F-16 Falcon Fighter Aircraft. Its purpose is for a failsafe redundant communication databus for use on military aircraft and other platforms.

Sital enhances this legacy technology with advanced features like Cyber Authentication, IDS/IPS (which includes BC Firewall), and wire fault detection and location. These aspects make it one of the safest and most secure communication systems available.

Can the BRM1553 IP-Core API be used in other OS than Windows?

The BRM1553 and other IP-Cores are provided with an API (set of functions) for Windows and Linux, written in native C and compiled with GCC compiler. The release includes drivers for Windows only and API source code that can be compiled to other Operating Systems like Integrity (some modifications might be required by the user).
Sital also provides commercial VxWorks drivers for the BRM1553 IP core and various Interface cards. These drivers are provided under license; please contact us for more details.

Which file should be used for the Arinc 429 IP-core?

“ARINC-429_*.*_API_Win32_Src.zip”

Can the tester handle 1553 and PP194 messages in the same frame?

Yes

What should the source sub-address be for my BC in COMposer?

In Mil-Std-1553, BC does not contain a sub-address, so there is no need to set it up in COMposer. Any settings will be ignored.

What OS/platforms does COMposer run on?

COMposer runs on WinXP, Win7-32/64bits, Win8/8.1-32/64bits and Windows 10 32/64 bits

What is Passive TDR (Ptdr)

TDR
Time-domain reflectometry or TDR is the ability to measure the distance to an electrical line fault based on reflections.
TDR analysis begins with the propagation of an energy impulse into the system and the subsequent observation of the energy reflected by the system.
When using TDR in a serial communication bus like a CAN bus, if the bus is intact, there are no reflections and all the energy turns to heat on the terminators.
In the case of a wire fault, there are reflections, whose delay depends on the propagation speed in the wires and the distance they traveled.
Sital’s off-the-shelf TDR tool transmits a pulse to the line, and measures the time to its reflection to estimate the distance in nanoseconds (ns) to the fault location.

Passive-TDR (pTDR)
Sital’s Passive TDR (pTDR) technology can estimate the distance to the wire fault without transmitting any signal to the bus!
pTDR derives the required information from the ongoing communications on the line without disturbing the ongoing bus activity.
When there is a bus disconnection, the reflections (from the ongoing signals) distort the communication signals and change their pulse width.
Measuring the distortion of a pulse width from its standard value provides the TDR information.
Passive TDR is the only TDR technique which does not send any signal to the bus (therefore it is called passive).
pTDR is being used to detect and locate wire faults such as disconnection and shorts.
Being able to run on live wires enables this technology to accurately detect and locate intermittent faults.

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