9XTend™
OEM
RF
Module
–
Product
Manual
v1.2.4
©
2005
MaxStream,
Inc.
Confidential
&
Proprietary
12
If RB or RO conditions are met, the module initializes a communications channel. Serial data in
the DI buffer is grouped into RF packets (up to 2048 bytes in each packet, refer to PK
Command), converted to RF data and is transmitted over-the-air until the DI buffer is empty.
Channel initialization is the process of sending an RF initializer that synchronizes receiving
modules with the transmitting module. During channel initialization, incoming serial data
accumulates in the DI buffer.
RF data, which includes the payload data, follows the RF initializer. The payload includes up to
the maximum packet size (PK Command) bytes. As the TX module nears the end of the
transmission, it inspects the DI buffer to see if more data exists to be transmitted. This could be
the case if more than PK bytes were originally pending in the DI buffer or if more bytes arrived
from the UART after the transmission began. If more data is pending, the transmitting module
assembles a subsequent packet for transmission.
Refer to the RF Communication Modes [p37] section to view state diagrams that illustrate
channel initialization and the sequence of events that follow.
RF Packet
Figure
2.6.
RF
Packet
Components
* When streaming multiple RF packets, the RF Initializer is only sent in front of the first packet.
RF Initializer
An RF initializer is sent each time a new connection sequence begins. The RF initializer contains
channel information that notifies receiving modules of information such as the hopping pattern
used by the transmitting module. The first transmission always sends an RF initializer.
An RF initializer can be of various lengths depending on the amount of time determined to be
required to prepare a receiving module. For example, a wake-up initializer is a type of RF
initializer used to wake remote modules from Sleep Mode (Refer to the FH, LH, HT and SM
Commands for more information). The length of the wake-up initializer should be longer than the
length of time remote modules are in cyclic sleep.
Header
The header contains network addressing information that filters incoming RF data. The receiving
module checks for matching a Hopping Channel, VID and Destination Address. Data that does not
pass through all three network filter layers is discarded.
Figure
2.7.
Network
Layers
Contained
in
the
Header