Codan Radio P25 Training Guide - Manual (Page 70)

TRAINING GUIDE | P25 RADIO SYSTEMS
Chapter 4: Anatomy of the Common Air Interface Page 62
Header CRC
The Header CRC is the CRC parity check for the Header Block
Data Block Serial Number
The Data Block Serial Number is an incremental serial number for each Data Block.
CRC-9
CRC-9 is the 9 bit CRC parity check for the Data Block.
Packet CRC
The packet CRC is the 4-octet CRC parity check coded over all of the User Data blocks (including the
User Data in the last block).
OTHER DATA FORMATS
Response Packet Format
The Response Packet is used to acknowledge (or not acknowledge) delivery for Confi rmed Data
Packets. The response packet contains fi elds called Class, Type and Status to specify the meaning of
the response.
Enhanced Addressing Format
Enhanced Addressing is used to send data directly between subscribers. A Source and Destination
address are both required on every packet. The SAP Identifi er is used to signify that a second address
is inserted in the packet before the user data.
Trunking Signaling Block (TSBK)
The Trunking Signaling Block (TSBK) is a special abbreviated data packet used for trunking control
channel messages. More detailed information on the TSBK can be found in Chapter 6: P25 Trunking.