CC2550_13 Datasheet, PDF (14/61 Pages) Texas Instruments – Low-Cost Low-Power 2.4 GHz RF Transmitter

CC2550
9 Configuration Software
CC2550 can be configured using the SmartRF^®
Studio software ([4]). The SmartRF^® Studio
software is highly recommended for obtaining
optimum register settings, and for evaluating
performance and functionality. A screenshot of
the SmartRF^® Studio user interface for CC2550
is shown in Figure 5.
After chip reset, all the registers have default
values as shown in the tables in Section 28.
The optimum register setting might differ from
the default value. After a reset all registers that
shall be different from the default value
therefore needs to be programmed through the
SPI interface.
Figure 5: SmartRF^® Studio [4] User Interface
10 4-wire Serial Configuration and Data Interface
CC2550 is configured via a simple 4-wire SPI-
compatible interface (SI, SO, SCLK and CSn)
where CC2550 is the slave. This interface is
also used to write buffered data. All transfer on
the SPI interface are done most significant bit
first.
All transactions on the SPI interface start with
a header byte containing a R/W bit, a burst
access bit (B), and a 6-bit address (A₅ – A₀).
The CSn pin must be kept low during transfers
on the SPI bus. If CSn goes high during the
transfer of a header byte or during read/write
from/to a register, the transfer will be
cancelled. The timing for the address and data
transfer on the SPI interface is shown in Figure
6 with reference to Table 14.
When CSn is pulled low, the MCU must wait
until CC2500 SO pin goes low before starting to
transfer the header byte. This indicates that
the crystal is running. Unless the chip was in
the SLEEP or XOFF states, the SO pin will
always go low immediately after taking CSn
low.
SWRS039B
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