CC1010 Datasheet, PDF (91/152 Pages) Texas Instruments – Single Chip Very Low Power RF Transceiver with 8051-Compatible Microcontroller

CC1010
17.6 Data Modem and Data Modes
Four different data modes are defined for
transmission and reception, programmable
through MODEM0.DATA_FORMAT. These
modes differ in data encoding, how
incoming and outgoing data is delivered
and
accepted,
and
whether
resynchronisation of the bitstream is
performed (clock regeneration) or not. The
data format should be selected before
enabling the RF Transceiver
Two of the modes, Synchronous NRZ
mode and Synchronous Manchester
encoded mode, transmit or receive data
using a baudrate as specified in
MODEM0.BAUDRATE. The modem does
resynchronisation of the bit stream during
reception. In the Manchester mode the
modem also does the Manchester
encoding and decoding. The NRZ and
Manchester modes accept and deliver
data either one bit or one byte at a time,
programmable
through
RFCON.BYTEMODE. In most applications
these two modes are recommended.
Data to be transmitted or data received
are stored in the RFBUF register. During
transmission or reception the need for
more data or the arrival of new data, bit by
bit or byte by byte depending on
RFCON.BYTEMODE, is signaled by
generating an interrupt (EXIF.RFIF.)
Depending on whether the RF interrupt is
enabled or not (EIE.RFIE), transmission
or reception can be handled by an
interrupt service routine or be performed
by polling.
During reception when using NRZ or
Manchester mode, hardware preamble
and start of frame detection can optionally
be activated using the registers PDET and
BSYNC. This is described in the
Synchronization and preamble detection
section on page 102.
Two other modes, Transparent mode and
UART mode, simply passes data between
the FSK modem and the RFBUF register
and UART0, respectively, allowing custom
baud rates and data encoding. When
using the UART0 in the UART mode the
pin P3.1 is not used for UART output and
can instead be used for general I/O.
Chipcon strongly recommends that the
synchronous modes be used. The other
data modes bypass the data decision
circuitry of the RF transceiver and do not
support bytemode. The Transparent mode
is only intended for testing.
17.6.1 Manchester encoding
In Manchester mode the data clock is
transmitted along with the data. A '1' is
encoded as a high frequency f₁ followed
by a lower frequency f₀. A '0' is encoded
as a low frequency f₀ followed by a higher
frequency f₁. This is illustrated in Figure
23. See the Frequency programming
section on page 106 for definitions of f₀
and f₁.
The Manchester code ensures that the
signal has a constant DC component,
which is necessary in some FSK
demodulators. Using this mode also
ensures compatibility with CC400 / CC900
designs.
The properties of the different data modes
are summarized in Table 29.
SWRS047
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