SLAU723A October 2017 – October 2018 MSP432E401Y , MSP432E411Y
GPIO Pulldown Select (GPIOPDR)
The GPIOPDR register is the pulldown control register. When a bit is set, a weak pulldown resistor on the corresponding GPIO signal is enabled. Setting a bit in GPIOPDR automatically clears the corresponding bit in the GPIO Pullup Select (GPIOPUR) register (see Section 17.5.15).
The table below shows special consideration GPIO pins. Most GPIO pins are configured as GPIOs and high-impedance by default (GPIOAFSEL = 0, GPIODEN = 0, GPIOPDR = 0, GPIOPUR = 0, and GPIOPCTL = 0). Special consideration pins may be programed to a nonGPIO function or may have special commit controls out of reset. In addition, a Power-On-Reset (POR) returns these GPIO to their original special consideration state.
| GPIO Pins | Default Reset State | GPIOAFSEL | GPIODEN | GPIOPDR | GPIOPUR | GPIOPCTL | GPIOCR |
|---|---|---|---|---|---|---|---|
| PC[3:0] | JTAG/SWD | 1 | 1 | 0 | 1 | 0x1 | 0 |
| PD[7] | GPIO(1) | 0 | 0 | 0 | 0 | 0x0 | 0 |
| PE[7] | GPIO(1) | 0 | 0 | 0 | 0 | 0x0 | 0 |
The GPIO commit control registers provide a layer of protection against accidental programming of critical hardware signals including the GPIO pins that can function as JTAG/SWD signals and the NMI signal. The commit control process must be followed for these pins, even if they are programmed as alternate functions other than JTAG/SWD or NMI; see Section 17.3.4.
NOTE
If the device fails initialization during reset, the hardware toggles the TDO output as an indication of failure. Thus, during board layout, designers should not designate the TDO pin as a GPIO in sensitive applications where the possibility of toggling could affect the design.
NOTE
The GPIO commit control registers provide a layer of protection against accidental programming of critical hardware peripherals. Protection is provided for the GPIO pins that can be used as the four JTAG/SWD pins and the NMI pin (see for pin numbers). Writes to protected bits of the GPIO Alternate Function Select (GPIOAFSEL) register (see Section 17.5.10), GPIO Pullup Select (GPIOPUR) register (seeSection 17.5.15), GPIO Pulldown Select (GPIOPDR) register (see Section 17.5.16), and GPIO Digital Enable (GPIODEN) register (see Section 17.5.18) are not committed to storage unless the GPIO Lock (GPIOLOCK) register (seeSection 17.5.19) has been unlocked and the appropriate bits of the GPIO Commit (GPIOCR) register (see Section 17.5.20) have been set.
GPIOPDR is shown in Figure 17-20 and described in Table 17-25.
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| 31 | 30 | 29 | 28 | 27 | 26 | 25 | 24 | 23 | 22 | 21 | 20 | 19 | 18 | 17 | 16 | 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
| RESERVED | PDE | ||||||||||||||||||||||||||||||
| R-0x0 | R/W-0x0 | ||||||||||||||||||||||||||||||