CC2500
SWRS040C
Page 52 of 89
29 General Purpose / Test Output Control Pins
The three digital output pins
GDO0
,
GDO1
and
GDO2
are general control pins configured with
and
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
An on-chip analog temperature sensor is
enabled by writing the value 128 (0x80) to the
register. The voltage on
the
GDO0
pin
is
then
proportional
to
temperature. See Section 4.7 on page 14 for
temperature sensor specifications.
If the
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
signal goes
low.
If the
setting is 0x20 or
higher the
GDO
pins will work as programmed
also in SLEEP state. As an example,
GDO1
is
high
impedance
in
all
states
if
=0x2E.
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