Topic 6 Data Buses (Malaysian Institute of Aviation Technology PDF)

Malaysian Institute Malaysian Instituteof of Aviation Technology Aviation Technology TOPIC 6: DATA BUSES Revision 1 (FEB 2024)  Malaysian Institute...

Malaysian Institute Malaysian Instituteof of Aviation Technology Aviation Technology TOPIC 6: DATA BUSES Revision 1 (FEB 2024)  Malaysian Institute Malaysian Instituteof of Aviation Technology Aviation Technology By the end of this topic, student are able to: Understand the operation of data buses in aircraft systems, including knowledge of ARINC and other specifications Aircraft network/ Ethernet Revision 00 Issue 01 Module 5.4  Malaysian Institute Malaysian Instituteof of Aviation Technology Aviation Technology What is data buses? Aircraft data bus systems allow a wide variety of avionics equipment to communicate with one another and exchange data. Data buses are a wire or group of wires used to move data to/from components and to/from other computers. The data can be in form of electrical pulses or light signals (fibre optics) Revision 00 Issue 01 Module 5.4  Malaysian Institute of Aviation Technology BUS SYSTEM Bus system can be either unidirectional (one way) or bidirectional (two way). They can also be serial (one bit of data transmitted at a time) or parallel (often 8,16,32 bits of data at the same time). Bus system provide efficient means of exchange data between the diverse avionics system found in modern aircraft  Malaysian Institute of Aviation Technology BUS SYSTEM Example: Serial data Example: Parallel data  Malaysian Institute of Aviation Technology About ARINC ARINC - Aeronautical Radio INCorporated. A leading provider of transport communication & system engineering solution. Primary activity is to produce specifications and reports for purpose of: a) Indicating to manufacturers the group opinion concerning requisites of new equipment b) To channel new equipment designs in direction which will result in maximum standardization  Malaysian Institute Malaysian Instituteof of Aviation Technology Aviation Technology About ARINC Examples of ARINC specifications  ARINC 573 - Digital Flight data recording  ARINC 561 - Inertial Navigation Systems  ARINC 429 - Transfer digital data between avionic components  ARINC 629 - Improvement of ARINC 429 system  ARINC 636 – Fibre optic data bus Revision 00 Issue 01 Module 5.4  Malaysian Institute Malaysian Instituteof of Aviation Technology Aviation Technology What is ARINC 429 ? Is a specification which define how avionic equipment and systems should communicate each other. Point to point data bus and uses a unidirectional data bus standard (Tx and Rx are on separate ports). Specific title for ARINC 429 is MARK 33 DIGITAL INFORMATION TRANSFER SYSTEM (DITS). This specification describes a method of transmitting information from a designated output port to systems requiring Revision 00 Issue 01this informationModule 5.4  Malaysian Institute of Aviation Technology Consist of pair of twisted wires with shielding Messages are transmitted at either 12.5kbits/sec (low speed) or 100 kbit/s (high speed) to other system elements that are monitoring the bus messages. Always transmitting either 32-bit data words or the NULL state A typical system using the ARINC 429 format is the VHF communication system.  Malaysian Institute Malaysian Instituteof of Aviation Technology Aviation Technology ARINC 429 -Electrical Characteristic Self clocking and self synchronizing system called 'bipolar return to zero' Self-clocking: the receiver senses the null between bits to generate its internal clocking. Self-synchronising: the receiver senses the four bit null between words to generate word synchronisation. Transmitted in binary bit form, '1's and '0's are represent high voltage (+5v) and low voltage (-5v ) level respectively for half of clock cycle then each pulse return Revision to zero 00 Issue 01 in the middle of 5.4 Module clock pulse.  Malaysian Institute Malaysian Instituteof of Aviation Technology Aviation Technology ARINC 429 - Electrical Characteristic Revision 00 Issue 01 Module 5.4  Malaysian Institute Malaysian Instituteof of Aviation Technology Aviation Technology ARINC 429 -Protocol Only one transmitter on a wire pair Always transmit 32 bit word or NULL state One ARINC 429 transmitter can provide data to 20 ARINC receivers maximum. ARINC 429 data buses are uni-directional. Received depend on line length and the numbers of receivers connected to the bus. Revision 00 Issue 01 Module 5.4 Malaysian Institute of Aviation Technology Example of ARINC429 Application  Malaysian Institute of Aviation Technology Example of ARINC 429 Application in Boeing 747  Malaysian Institute Malaysian Instituteof of Aviation Technology Aviation Technology ARINC 429 - Word Format WORD format is a 32 bit with five basic parts - LABEL - SOURCE /DESTINATION IDENTIFIER (SDI) - DATA FIELD - SIGN STATUS MATRIX(SSM) - PARITY BIT (P) Revision 00 Issue 01 Module 5.4  Malaysian Institute Malaysian Instituteof of Aviation Technology Aviation Technology ARINC 429 - Word Format Revision 00 Issue 01 Module 5.4 Malaysian Institute of Aviation Technology ARINC 429 - Word Format  Malaysian Institute Malaysian Instituteof of Aviation Technology Aviation Technology ARINC 429 - Word Format (LABEL) LABEL - The first 8 bits of the word is expressed in three octal characters that are coded in binary. Identifies the information contained in the data e.g. airspeed, total air temp. The label is unique in that the least significant bit (LSB) is last in sequence. The label bits are therefore read in reverse order. Revision 00 Issue 01 Module 5.4  Malaysian Institute of Aviation Technology ARINC 429 - Word Format (LABEL) LABE PARAMETER L 230 True Airspeed 231 Total Air Temperature 233 Static Air Temperature 323 Flight Path Acceleration 330 Body Yaw Rate Example of label  Malaysian Institute of Aviation Technology ARINC 429 - Word Format (Label) Example of label  Malaysian Institute of Aviation Technology ARINC 429 – Word Format Source/Destination Identifier(SDI) SDI is used to identify the source/ destination of a word e. g. Which of a number of installations the word is coming from or needs to be directed into. When the information is sent to a specific location, the source equipment encodes the desired receiver’s installation number in bits 9 and 10.  Malaysian Institute Malaysian Instituteof of Aviation Technology Aviation Technology ARINC 429-Word Format (Data Field) DATA FIELD - contains specific data related to the LABEL. There are 2 format of data field ; For binary word contained in bits 11- 28 and binary coded decimal (BCD) in bits 11- 29. Any bit not used are filled with logic 0's (pad bits) Given in the example is in BCD format, the DME distance is 22.35 nautical miles. The decimal point placement is determined by the resolution. Revision 00 Issue 01 Module 5.4  Malaysian Institute of Aviation Technology ARINC 429-Word Format (Data Field)  Malaysian Institute Malaysian Instituteof of Aviation Technology Aviation Technology ARINC 429 - Word Format SSM code for identity characteristic of the word for BCD data Revision 00 Issue 01 Module 5.4  Malaysian Institute Malaysian Instituteof of Aviation Technology Aviation Technology ARINC 429 - Word Format (Parity Bit) PARITY - Uses odd parity e.g. Total number of logic '1' in the word must be an odd number. If not parity bit is set to 1. Uses to check an error e.g. If receiving signal doesn't contain odd number 1, fault signal will be generated.  Malaysian Institute Malaysian Instituteof of Aviation Technology Aviation Technology ARINC 429 - Transmission Order The least significant bit of each byte except the label is transmitted ahead of the data in each case. The order as follows: 8,7,6,5,4,3,2,1,9,10,11,12,13,14,....32. Revision 00 Issue 01 Module 5.4  Malaysian Institute of Aviation Technology ARINC 629 -General Description An ARINC 629 data bus is an electronic data movement system that connects many line replaceable units (LRUs) in a single communication loop. ARINC 629 is a newer digital data bus format that offers more flexibility and greater speed than the 429 system. The ARINC 629 data bus is a high speed, two way, multiple terminal digital data bus. Up to 120 terminals can be connected to the bus Data bus can be either an unshielded twisted pair of wires (up to 100m long)or a fiber optic cable.  Malaysian Institute of Aviation Technology ARINC 629 -General Description The Boeing Company, in developing the B777, anticipated the use of ARINC 629 in a two-wire format. ARINC 629 has two major improvements over the 429 system: First, there is a substantial weight saving. Second, the ARINC 629 data bus operates at speeds up to 2 Mbps. It uses a high speed bi- directional bus capable of either periodic or aperiodic transmissions.  Malaysian Institute Malaysian Instituteof of Aviation Technology Aviation Technology ARINC 629 -General Description Inductive coupling technique is used to connect the bus to receivers/transmitters. It uses electromagnetic induction to transfer current from the bus to the user, or from the user to the bus. This system improves reliability, since no break in the bus wiring is needed to form connections. Access to the bus is controlled by a sophisticated protocol involving wait periods, quiet periods and other rules.  Malaysian Institute of Aviation Technology ARINC 629 Each LRU or LRM that requires to be connected to the bus uses a current mode coupler. Up to 120 couplers can be connected to a bus cable  Malaysian Institute of Aviation Technology ARINC 636 : Fiber Optics The ARINC 636 is a fiber optic data bus. One strand of optical fiber per bus. Two strands of optical fiber provide a primary (PRI) and secondary (SEC) bus. The ARINC 636 fiber optic data bus connects to many LRU/LRMs. LRU/LRMs send and receive data in series on the ARINC 636 fiber optic data bus. An ARINC 636 LRU/LRM sends and receives data at 100 Mbps on the ARINC 636 data bus.