CC2550_06 Datasheet, PDF (32/55 Pages) Texas Instruments – Single Chip Low Cost Low Power RF Transmitter

CC2550
25 Asynchronous and Synchronous Serial Operation
Several features and modes of operation have
been included in the CC2550 to provide
backward compatibility with previous Chipcon
products and other existing RF communication
systems. For new systems, it is recommended
to use the built-in packet handling features, as
they can give more robust communication,
significantly offload the microcontroller and
simplify software development.
25.1 Asynchronous operation
For backward compatibility with systems
already using the asynchronous data transfer
from other Chipcon products, asynchronous
transfer is also included in CC2550. When
asynchronous transfer is enabled, several of
the support mechanisms for the MCU that are
included in CC2550 will be disabled, such as
packet handling hardware, buffering in the
FIFO and so on. The asynchronous transfer
mode does not allow the use of the data
whitener, interleaver and FEC.
Only FSK, GFSK and OOK are supported for
asynchronous transfer.
Setting PKTCTRL0.PKT_FORMAT to 3
enables asynchronous transparent (serial)
mode.
In TX, the GDO0 pin is used for data input (TX
data).
The MCU must control start and stop of
transmit with the STX and SIDLE strobes.
The CC2550 modulator samples the level of the
asynchronous input 8 times faster than the
programmed data rate. The timing requirement
for the asynchronous stream is that the error in
the bit period must be less than one eighth of
the programmed data rate.
25.2 Synchronous serial operation
Setting PKTCTRL0.PKT_FORMAT to 1
enables synchronous serial operation mode. In
this operational mode the data must be NRZ
encoded (MDMCFG2.MANCHESTER_EN=0). In
synchronous serial operation mode, data is
transferred on a two wire serial interface. The
CC2550 provides a clock that is used to set up
new data on the data input line. Data input (TX
data) is the GDO0 pin. This pin will
automatically be configured as an input when
TX is active.
Preamble and sync word insertion may or may
not be active, dependent on the sync mode set
by the MDMCFG3.SYNC_MODE. If preamble and
sync word is disabled, all other packet handler
features and FEC should also be disabled.
The MCU must then handle preamble and
sync word insertion in software. If preamble
and sync word insertion is left on, all packet
handling features and FEC can be used. The
CC2550 will insert the preamble and sync word
and the MCU will only provide the data
payload. This is equivalent to the
recommended FIFO operation mode.
26 System considerations and Guidelines
26.1 SRD Regulations
International regulations and national laws
regulate the use of radio receivers and
transmitters. Short Range Devices (SRDs) for
license free operation are allowed to operate
in the 2.45 GHz bands worldwide. The most
important regulations are EN 300 440 and EN
300 328 (Europe), FCC CFR47 part 15.247
and 15.249 (USA), and ARIB STD-T66
(Japan). A summary of the most important
aspects of these regulations can be found in
Application Note AN032 SRD regulations for
license-free transceiver operation in the 2.4
GHz band, available from the TI and Chipcon
websites.
Please note that compliance with regulations
is dependent on complete system
performance. It is the customer’s responsibility
to ensure that the system complies with
regulations.
26.2 Frequency Hopping and Multi-
Channel Systems
The 2.400 – 2.4835 GHz band is shared by
many systems both in industrial, office and
home environments. It is therefore
recommended to use frequency hopping
spread spectrum (FHSS) or a multi-channel
protocol because the frequency diversity
makes the system more robust with respect to
PRELIMINARY Data Sheet (Rev.1.2) SWRS039A
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