MIL-STD-1553 design was initially for control of military aircraft. Hence, the protocols and connections of gadgets and systems offered robust, reliable, and redundant solutions.
MIL-STD-1553 is a military standard that defines the characteristics of a serial data bus, and the US Department of Defense has published it. MIL-STD-1553 standard defines mechanical, electrical, and functional aspects of the serial data bus. The MIL-STD-1553 combines both physical and protocol standards, making it suitable for aerospace systems.
1. Data Speed
MIL-STD-1553 uses a one megabit per sec data rate which is adequate for a large number of applications. However, other systems require higher speeds.
2. Features of MIL-STD-1553
MIL-STD-1553 features include;
- Multiple redundant balanced line physical layers
- A network interface
- Time-division multiplexing
- Half-duplex command or response protocol
MIL-STD-1553 was a US air force standard; however, both military planes and civil aviation are currently using the standard.
3. Physical Layer Standard
Allows a bus to have a single wire with an impedance of 70-85 ohms at a speed of 1MHz. In a circular connector, the center is the center pin becomes the bi-phase signal. The transmitters and receivers transfer energy to the bus through isolation transformers.
4. MIL-STD-1553 Advantages for Time-Triggered Networks
MIL-STD-1553 offers many advantages for time-triggered networks, which include;
- Differential signaling offers defined idle time to prevent collisions between consecutive transmitters.
- MIL-STD-1553 uses transformer isolation and optional transformer bus coupling, thus offering several advantages.
- The MIL-STD-1553 is suitable in relatively harsh conditions. Hence, the serial data bus has to be fault-tolerant, making MIL_STD_1553 ideal for systems in commercial aircraft.
5. Advantages of Transformer Bus Coupling in MIL-STD-1553
- DC isolation
- Common mode rejection
- Lightning protection
- Isolation resistors that are in series protect from short circuit faults.
- Transformer bus coupling increases stub impedance for increased stub lengths.
- The high transmit voltages of MIL-STD-1553 provide a robust data rate and cable length performance.
6. MIL-STD-1553 Specifications
- Output noise
- Transmitter zero-crossing distortion
7. The MIL-STD-1553 Voltage States
MIL-STD-1553 sets differential signaling with three states, namely;
- Idle state
- Active high
- Active low
Idle State of Voltage
- The idle voltage enables receivers to determine the idle time, indicating its time to transmit to the next bus. Idle voltage helps prevent collision within the preceding nodes.
- The signal encoding method for MIL-STD-1553 is Manchester bi-phase.
8. Advantage of Differential Bus
The use of a differential bus instead of the single-end bus has the advantage of providing common-mode performance and lightning immunity. Hence a short circuit can’t bring down the whole system due to the protection MIL-STD-1553 offers by using a differential.
9. Advantages of Transformer Isolation
- Provides strength in DC isolation
- Ability to survive lightning.
- Common mode rejection
Note that common-mode rejection is essential in reducing noise along transmission lines.
10. MIL-STD-1553 Cable Specifications
- The cable specifications for MIL-STD-1553 include;
- Cable with twist and shield- 75% shield minimum
- Cable with a characteristic impedance- 70-85 ohms at 1MHz
- Cable-line with maximum attenuation-1.5 dB/100ft at 1MHz
- Capacitance- 30pF/ft., maximum
11. MIL-STD-1553 Applications
- Attack in fighter planes
- Flight control
- Mission computers
- Weapon control for fighters
- Transport aircraft
MIL-STD-1553 is a military standard that defines the electrical, functional, and mechanical characteristics of serial data buses used in avionics and aircraft. The physical layer that MIL-STD-1553 defines are suitable for time-triggered networking technologies. Idle voltages are vital in preventing collisions between two consecutive transmitters, thus enhancing effective communication and safety.