SN250 datasheet(32/130 Pages) STMICROELECTRONICS

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Functional description—application modules

SN250

32/130

Figure 5.

GPIO control logic

The GPIO_DBG register must always remain set to zero. The GPIO_CFG register controls

the GPIO signal routing for alternate GPIO functions as listed in Table 17. Refer to Table 1

for individual pin alternate functions.

Table 18 defines the alternate functions routed to the GPIO. To allow more flexibility, the

timer signals can come from alternative sources (e.g., TIM1IA.1, TIM1IA.2, TIM1IA.3),

depending on what serial controller functions are used.

The Always Connected input functions labelled IRQA, IRQB, IRQC and IRQD refer to the

external interrupts. GPIO8, GPIO14, GPIO15, and GPIO16 are the only pins designed to

operate as external interrupts (IRQs). These pins offer individual filtering options, triggering

options, and interrupt configurations. The minimum width needed to latch an unfiltered

external interrupt in both level and edge triggered mode is 80ns. With the filter engaged via

the GPIO_INTFIlT bit, the minimum width needed in 450ns. Other alternate functions such

as timer input captures are capable of generating an interrupt based on external signals, but

these other alternate functions do not contain the flexibility offered on the four external

interrupts (IRQs).

When the core is powered down, peripherals stop driving correct output signals. To maintain

correct output signals, the system software will ensure that the GPIO output signals are

frozen before going into deep sleep.

Monitoring circuitry is in place to detect when the logic state of GPIO input pins change. The

lower 16 GPIO pins that should be monitored can be chosen by software with the

GPIO_WAKEL

described in Section 6.14.

Alternate

GPIO

functions

GPIO[16:0]

VDD_PADS

GPIO_CFG

GPIO_INH/L

GPIO_SETH/L

GPIO_DIRSETH/L

GPIO_PUH/L

GPIO_PDH/L

GPIO_CLRH/L

GPIO_DIRH/L

GPIO_DIRCLRH/L

GPIO_OUTH/L

Note (1)

Note (2)

Pull-up resistor is always disabled for Alternate GPIO functions ADC 0,

ADC1, ADC2, ADC3, VREF_OUT, PTI_EN and PTI_DATA.

Note (1) :

Pull-down resistor is always disabled for Alternate GPIO functions

VREF_OUT, PTI_EN and PTI_DATA.

Note (2) :

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