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29 General Purpose / Test Output Control Pins
The three digital output pins GDO0, GDO1 and
GDO2 are general control pins configured with
IOCFG0.GDO0_CFG,
and IOCFG2.GDO2_CFG respectively. Table
33 shows the different signals that can be
monitored on the GDO pins. These signals can
be used as inputs 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 135-141 kHz
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.
An on-chip analog temperature sensor is
enabled by writing the value 128 (0x80) to the
IOCFG1.GDO1_CFG
SWRS040C
IOCFG0.GDO0_CFG register. The voltage on
the
pin
is
GDO0
temperature. See Section 4.7 on page 14 for
temperature sensor specifications.
If the IOCFGx.GDO0_CFG setting is less than
0x20 and IOCFGx_GDOx_INV is 0 (1), the
GDO0 and GDO2 pins will be hardwired to 0 (1)
and the GDO1 pin will be hardwired to 1 (0) in
the SLEEP state. These signals will be
hardwired until the CHIP_RDYn signal goes
low.
If the IOCFGx.GDO0_CFG setting is 0x20 or
higher the GDO pins will work as programmed
also in SLEEP state. As an example, GDO1 is
high
impedance
IOCFG1.GDO0_CFG=0x2E.
CC2500
then
proportional
to
in
all
states
Page 52 of 89
if
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