Installation
Becker Avionics
Targets Status Protocol - IF3 Interface
80
BD406/PBD406
DV16401.03 Issue 04 May 2021
Packet CRC Definition
•
Packet CRC shall be calculated using 16-bit binary polynomial represented by number
0x8005 (known as CRC-16).
•
Packet CRC shall be calculated from sequence of bits consisting of packet header,
protocol ID, frame length and frame.
•
Bits shall be inserted for packet CRC calculation starting from the MSB of the packet
header.
Examples of calculated checksums:
•
Input: 0x0000
result: 0x0000
•
Input: 0x0001
result: 0x8005
•
Input: 0x0001 0x8005
result: 0x0000
•
Input: 0xFFFF
result: 0x800D
•
Input: 0xA514 0x0120
result: 0x43E3
Maximal Duration of the Transmitted Packet
Duration of outgoing packet is no longer than twice the minimum time required for packet
transmission:
[Max packet duration] <= 20 * [1/bit rate] * [number of bytes in the packet]
Recommended Receiver Operation
Incoming Packet
•
The receiver scans for the packet header, record the packet and verify the packet CRC.
•
Packets with incorrect CRC will be rejected.
Packet is valid if:
•
Frame ID is correct for protocol ID extracted from packet and
•
The length of the received frame is correct.
Otherwise the frame is invalid. Invalid frames will be ignored.
Length of the Longest Supported Packet
The receiver can work with packets which length is not larger than 75 bytes.
