The STEDS Message 26 Text Message format provides for both a broadcast and addressed text message. The text may be up to 141 6-bit ASCII characters (up to 846 bits). Message addressing, when required, shall be performed using the Destination Indicator and Destination ID fields inherent to the Message 26 structure.
|
Parameter |
Number of bits |
Description |
Encryption Status |
|
Function ID |
5 |
0 = Text Message |
AES encrypted |
|
Hour |
5 |
0-23 |
AES encrypted |
|
Minute |
6 |
0-59 |
AES encrypted |
|
Second |
6 |
0-59 |
AES encrypted |
|
Text Length |
8 |
Length of the text message, expressed as the number of 6-bit ASCII characters |
AES encrypted |
|
Text |
0-846 bits Variable |
Maximum number of 6-bit ASCII characters is 141 for both message types. |
AES encrypted |
|
Unused bits set to zero |
Variable |
Unused bits set to zero are inserted so that the number of bits in the encrypted field is a multiple of 128 bits. |
AES encrypted |
|
Checksum |
16 |
Cyclic Redundancy Check (CRC) 16-bit polynomial |
AES encrypted |
|
TOTAL |
128 256 384 512 640 768 896 |
128, 256, 384, 512, 640, 768 or 896 encrypted bits |
AES encrypted |
