AN2262 Motorola / Freescale Semiconductor, AN2262 Datasheet - Page 26

• Manufacturer Part Number: AN2262
• Description: Wireless HC08 Modem
• Manufacturer: Motorola / Freescale Semiconductor

AN2262/D
RF-08 Protocol
CRC Security
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Figure 16
The RF-08 protocol used in this application is truly simple. Every frame sent
over RF consists of three fields:
The RF-08 protocol is shown on
The cyclic redundancy codes method (also known as polynomial codes) is
used to verify the integrity of every frame sent over the RF medium. An
additional field is appended to every data block at the time of transmission
and is checked at the time of reception for correctness. One of the well known
16-bit CRC polynomials called CRC-16, is used in the RF-08 application:
1. A length field (8 bit value), the length of a complete frame including the
2. Data (variable length), limited by memory restrictions of the CPU
3. A CRC field (16 bits)
‘PREAMBLE’ FLAG
x
RF TRANSMISSION
RF-08 PROTOCOL
‘HEADER’ FLAG
16
LENGTH
8 BITS
+ x
‘TAIL’ FLAG
length and CRC fields.
transmit and receive buffers, also limited by 255 bytes (maximum value
of length field)
15
shows the interaction between all special TX flags:
+ x
2
+ 1
Wireless HC08 Modem
PREAMBLE
Figure 16. Special TX Flag Interactions
Figure 17. RF-08 Protocol
HEADER
VARIABLE LENGTH
Figure
DATA
17.
DATA (PAY-LOAD)
16 BITS
CRC
MOTOROLA
TAIL