CC2570 Datasheet, PDF (14/32 Pages) Texas Instruments – 1- and 8-Channel ANT™ RF Network Processors

CC2570
CC2571
SWRS095A – FEBRUARY 2011 – REVISED MARCH 2011
www.ti.com
Table 2. Baud Rate Selection
Baud Rate
BR1
BR2
BR3
57,600
1
1
1
50,000
1
1
0
38,400
1
0
0
19,200
0
1
0
9,600
1
0
1
4,800
0
0
0
The asynchronous serial interface supports unidirectional hardware flow control. As indicated in Figure 8, the
RTS line from the CC257x should be connected to the CTS line of the host MCU. The host MCU must halt the
sending of any messages while the RTS signal is asserted. Note that the RTS signal is briefly asserted following
every message received by ANT on the serial port. The length of this pulse is approximately 50 µs. Any bytes
sent while RTS is high are ignored by ANT. For this reason, it is recommended that two padding bytes or a
reasonable delay be inserted between serial messages. This is especially important when sending burst serial
messages to ANT.
USE OF SLEEP AND SUSPEND
To ensure lowest power operation, the host MCU must control the power state of the CC257x explicitly using the
SLEEP and SUSPEND signal lines. Review the ANT document Interfacing with ANT General Purpose Chipsets
and Modules and the Application note Power States for complete details on how these signals should be used.
The SLEEP signal should be used to put the CC257x into its lowest state when serial communication is not
required. This is accomplished by asserting the SLEEP signal between any serial messages being sent from the
host MCU to ANT. This is illustrated by the timing diagram in Figure 9.
HOST MCU
CC257x
SLEEP
(Output)
SLEEP
(Input)
HOST_CTS
(Input)
RTS
(Output)
HOST_TX
(Output)
RX
(Input)
Figure 9. Use of Sleep
T0497-01
Regardless of the state of the SLEEP signal, ANT sends any messages to the host MCU immediately.
The SUSPEND signal should only be used in USB applications where the USB specification requires that the
MCU be put into a known low power state very quickly. Asserting SUSPEND terminates all RF activity,
regardless of the state of ANT. Entering and exiting the suspend state requires the use of the SLEEP signal as
depicted in Figure 10.
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