CC2550 Datasheet, PDF (30/50 Pages) Texas Instruments – Single Chip Low Cost Low Power RF-Transmitter

The passive matching/filtering network
connected to CC2550 should have the following
differential impedance as seen from the RF-
port (RF_P and RF_N) towards the antenna:
Z_out = 80 + j74 Ω
31 General Purpose / Test Output Control Pins
The two digital output pins GDO0 and GDO1 are
general control pins. Their functions are
programmed by IOCFG0.GDO0_CFG and
IOCFG1.GDO1_CFG respectively. Table 23
shows the different signals that can be
monitored on the GDO pins. These signals can
be used as an interrupt to the MCU. GDO1 is
the same pin as the SO pin on the SPI
interface, thus the output programmed on this
pin will only be valid when CSn is high. The
default value for GDO1 is 3-stated, which is
useful when the SPI interface is shared with
other devices.
The default value for GDO0 is a 125kHz-
146kHz clock output (XOSC frequency divided
by 192). Since the XOSC is turned on at
power-on-reset, this can be used to clock the
MCU in systems with only one crystal. When
the MCU is up and running, it can change the
clock frequency by writing to
IOCFG0.GDO0_CFG. This will not produce
any clock glitches.
An on-chip analog temperature sensor is
enabled by writing the value 128 (0x80h) to the
IOCFG0.GDO0_CFG register. The voltage on
the GDO0 pin is then proportional to
temperature. See section 9 on page 8 for
temperature sensor specifications.
CC2550
Preliminary Data Sheet (rev. 1.1) SWRS039
Page 30 of 51