User's Manual
Table Of Contents
- 1. Introduction
- 2. Hardware
- 3. The A431 Radio Module
- 3.1. About the A431 Radio Module
- 3.2. Functional description
- 3.3. Manufacturing Issues
- 3.3.1. Marking and labeling issues
- 3.3.2. Alignment Range and Switching Range
- 3.3.3. Tuning Procedure
- 3.3.4. Setting Up the Default Parameters
- 3.3.5. Definitions
- 3.3.6. Test Equipment Settings
- 3.3.7. Trimming Elements
- 3.3.8. Adjusting the Receiver Front End
- 3.3.9. Adjusting the VCOs
- 3.3.10. Adjusting the Crystal Reference
- 3.3.11. Checking the Receiver Parameters
- 3.3.12. Checking the Transmitter Parameters
- 3.3.13. Data Transfer Check
- 3.6. Frequency Reference Specifications
- 3.7. A431 Module’s Photographs
- 4. Software
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Data Frames
4.4.4. Data Frames
The data frames (payload) are the blocks of data extracted from the radio frames,
after the CRC and other information (source address) was checked. The data frame
and its length are passed to the upper layers of the software.
Figure 25. Generic Data Frame structure.
A data frame is composed of two main parts: a header, containing the frame type as
well as the routing information, and a data block. The length of the data block can
be easily computed by subtracting the header length (HLEN + 1 byte for the TYPE)
from the original data frame length received from the lower layer of the software (the
radio frame length). Additional explanations on the notation used in the diagram:
• TYPE is the type of frame.
• HLEN is the header length: it represents the number of bytes used to de-
scribe the route the frame will go (or went). The maximum number of hops is
8, that is, 8 intermediate stations plus source and destination. Each station is
described by its unique 16-bit address.
• SRC, HOP and DEST, are the source, the hops and the destination addresses.
While the hops may be missing (no routing stations between source and des-
tination), the source and destination are mandatory.
• DATA is the data proper field. It is limited in length, its maximum size being
dependent also on the particular route: if the route is longer (8 hops) then the
data block is limited to 48 bytes. Depending on the frame type, the data block
may be nonexistent (zero length).
TYPE HLEN SRC-H
SRC-L
.......
HOP1-H HOP1-L HOPn-H HOPn-L DEST-LDEST-H DATA1 DATA2 DATAn
.......
Header (Frame Type + Routing Information)
Data