User`s manual

checking. Data is encoded using a proprietary algorithm (DirectSPREAD™) to spread the RF
energy equally within the transmission bandwidth.
Modules can operate in groups. Each module can be assigned an 8-bit group ID, which is used
to logically link it to other modules on the same channel. All modules on a channel will
interoperate, regardless of their respective group Ids. In other words, the CSMA mechanism will
prevent collisions of modules on the same channel but belonging to different groups.
Modules can also operate in two network modes: Master/Slave and Peer-to-Peer. These modes
define a set of communication rules that identifies which modules can talk to any given module.
In Master/Slave mode, masters can talk to slaves and other masters, slaves can talk to masters,
but slaves cannot talk to other slaves. This mode is sometimes required for applications that are
replacing legacy RS-485 networks. In peer-to-peer mode, any module can hear any other
module. In both modes, group integrity is enforced.
When a module transmits a packet, all other modules on the same channel will receive the
packet, check the packet for errors, and determine whether the received group ID matches the
local group ID. If the packet is error free and the group Ids match, the module will decrypt the
data if necessary, and send the error free data to its host UART for processing. The modules
only implement the ISO reference network stack up to the MAC layer, so they are transparent to
link layer addressing schemes. Therefore, the modules can work with any link-layer and higher
protocols in existing today.
Certain features of the module are controlled through programmable registers. Registers are
access by bringing CMD low. When CMD is low, all data transfers from the host UART are
considered to be register access commands. When CMD is high, all data transfers from the host
UART are considered to be raw data that needs to be transparently transmitted across the
wireless link. The module maintains two copies of each register: one in flash and one in RAM.
On reset, the module loads the RAM registers from the values in the flash registers. The module
is operated out of the RAM registers. Applications that need to change parameters of the module
often would simply modify the RAM register. By putting default settings in the flash registers, the
module will always come up in a preconfigured state, which is useful for applications that do not
have external microcontrollers, such as RS-232 adapters.
The UART interface is capable of operating in full duplex at baud rates from 2.4 to 115.2 kbps.
The module has six power modes: High DTS, Medium DTS, Low DTS, low power, standby, and
sleep.
The Wi.232DTS module is the first module in the world to take advantage of the digital spread
spectrum provision in FCC part 15 rules. Under this provision, transmitters can operate at a
higher output power if the transmission bandwidth is at least 500kHz. Through an encoding
technique we call DirectSPREAD™, the Wi.232DTS module is able to operate at +11dBm and
meet the requirements of this provision.
In DTS mode, the module’s channel bandwidth is set to 600kHz and the transmit power is set to
+11dBm. In this mode, the module can operate on 32 channels and support a maximum RF data
rate of 152.34kbit/second. The receiver sensitivity at the max data rate is –100dBm typical,
yielding a link budget of 111dB. This mode is an excellent alternative to frequency hopping
spread spectrum. It has very fast synchronization, allowing it to operate in a duty-cycle mode for
extended battery life.
In low-power mode, the module’s channel bandwidth is set to 200kHz and the transmit power is
set to 0dBm. In this mode, the module can operate on 84 channels and support a maximum data
rate of 38.4 kbit/second. The receiver sensitivity at the maximum data rate is –105 typical,
yielding a link budget of 105dB. This mode reduces transmit current consumption, allowing use
Wi.232DTS © 2003-2005 Radiotronix Inc. 7
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