CC2520_11 Datasheet, PDF (36/133 Pages) Texas Instruments – 2.4 GHZ IEEE 802.15.4/ZIGBEE RF TRANSCEIVER

CC2520 DATASHEET
2.4 GHZ IEEE 802.15.4/ZIGBEE® RF TRANSCEIVER
SWRS068 – DECEMBER 2007
11.3 GPIO as Output
When a GPIO pin is configured as an output, the signal corresponding to the CTRLn setting in GPIOCTRLn
register (CTRLn values are shown in Table 8 in section 12.6). The polarity of the pin is set in the
GPIOPOLARITY register.
Example: Set up GPIO3 to output sniff_data with active high level indication.
• Set GPIOPOLARITY[3] to ‘1’’. GPIO pin 3 set to active high level indication.
• Set GPIOCTRL3[7:0] to “0011 0010”. GPIO pin 3 is now an output and outputs sniff_data.
11.4 Switching Direction on GPIO
When switching from output to input, care must be taken so that command strobes are not triggered
unintentionally. Changing GPIOn to a command strobe triggering input (one of the first 16 entries in Table 8)
needs to be done using the following procedure to avoid changing direction while the pin is high:
1. Write 0x7E to GPIOCTRLn to make it output a constant 0.
2. Drive a ‘0’ from the microcontroller to the GPIO pin.
3. Write for instance 0x88 to GPIOCTRLn to change to input that triggers the STXON command
strobe.
11.5 GPIO Configuration
Table 8 summarizes the signals that are available as output on any GPIO pin. The CTRLn column shows
the configuration value that needs to be written to any one of the GPIOCTRL0-GPIOCTRL5 registers in
order to get the described functionality. The IN column in Table 8 shows which command strobe that will be
executed if the GPIO is configured as input and an edge (with the correct polarity) is applied. The OUT
column shows the name of the internal signal that is observable on the pin if the GPIO is configured as an
output.
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