CC2570 Datasheet, PDF (6/32 Pages) Texas Instruments – 1- and 8-Channel ANT™ RF Network Processors

CC2570
CC2571
SWRS095A – FEBRUARY 2011 – REVISED MARCH 2011
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ANT Channel Types
There are different types of ANT channels, including bidirectional channels, unidirectional channels, shared
channels, and scanning channels. The type of channel chosen for a particular application is dependent on the
application requirements for use case, power consumption, topology, and battery life expectancy.
Bidirectional channels support two-way communication between the master and the slave. The master transmits
a message on every channel period, whereas the slave only transmits a message to the master if required to do
so by the application. For every message that the slave receives from the master, the slave can transmit a
message back. Hence, the effective data through put is the same in both directions. Bidirectional channels are
also necessary to take advantage of ANT’s unique channel co-existence mechanisms.
Unidirectional, or transmit-only, channels allow for communication from the master to the slave only. These types
of channels support the broadcast message type only and do not offer the co-existence mechanisms built into
bidirectional channels. Although unidirectional channels provide the lowest power solution, they are generally not
recommended for systems that require co-existence of several ANT channels in a common RF space.
Shared channels are a special type of bidirectional channel that allow a single master endpoint to address up to
64K slaves. Each slave synchronizes to the channel period of the master. The master can address a different
slave on each channel timeslot by specifying the address of the slave in the first 2 bytes of the data payload. The
master may also send a broadcast message to all of the slaves simultaneously by specifying an address of 0.
Shared channels are an excellent solution for networks that require many of nodes and are sensitive to power
requirements but not to latency requirements.
Unidirectional
Bidirectional
...
Shared
Figure 5. Synchronous ANT Channel Types
M0213-01
Unlike the channel types listed previously, scanning channels are different in that they are asynchronous. That is,
the slave does not synchronize to a master channel. Instead, any message received from a master is passed
onto the application MCU, along with the channel ID of the device received from. This allows a slave to receive
from multiple masters without actually forming a connection to any particular master. Scanning channels come in
two flavors – continuous-scanning and background-scanning. The difference between the two amounts to a
tradeoff between power consumption and latency. A continuous-scanning channel keeps its receiver on all the
time. This means that any transmissions are received immediately, eliminating latency at the cost of power
consumption to keep the radio on all the time. Continuous-scanning channels are an ideal solution for systems
that must be very low power on one side of the link but not the other, for example, a remote control. A
background scanning channel does not keep its receiver on all of the time. Instead, it continually searches for
transmissions, without ever actually synchronizing to a channel. The power consumption is drastically reduced at
the expense of data latency. Background scanning channels are ideal for battery-operated systems where the
hub must be able to communicate with multiple nodes with reasonable latency, for example, a proximity
awareness application.
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