EM341-RTR datasheet(51/237 Pages) SILABS

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EM341

Rev 1.0

is exited and the normal program begins execution. In summary, the nBOOTMODE signal must be held low for

4 ms in order to properly invoke the FIB monitor.

After nBOOTMODE has been sampled, PA5 is configured as a floating input like the other GPIO configurations.

The GPIO_BOOTMODE bit in the GPIO_DBGSTAT register captures the state of nBOOTMODE so that software

may act on this signal if required.

Note: To avoid inadvertently asserting nBOOTMODE, PA5’s capacitive load may not exceed 250 pF.

7.6. GPIO Modes

7.6.1. Analog Mode

Analog mode enables analog functions, and disconnects a pin from the digital input and output logic. Only the

following GPIO pins have analog functions:



PA4, PA5, PB5, PB6, PB7, and PC1 can be analog inputs to the ADC.



PB0 can output the internal analog voltage reference from the ADC.



PC6 and PC7 can connect to an optional 32.768 kHz crystal.

Note: When an external timing source is required, a 32.768 kHz crystal is commonly connected to PC6 and PC7. Alternatively,

when PC7 is configured as a digital input, PC7 can accept a digital external clock input.

When configured in analog mode:



The output drivers are disabled.



The internal pull-up and pull-down resistors are disabled.



The Schmitt trigger input is connected to a high logic level.



Reading GPIO_PxIN returns a constant 1.

7.6.2. Input Mode

Input mode is used both for general purpose input and for on-chip peripheral inputs. Input floating mode disables

the internal pull-up and pull-down resistors, leaving the pin in a high-impedance state. Input pull-up or pull-down

mode enables either an internal pull-up or pull-down resistor based on the GPIO_PxOUT register. Setting a bit to 0

in GPIO_PxOUT enables the pull-down and setting a bit to 1 enables the pull up.

When configured in input mode:



The output drivers are disabled.



An internal pull-up or pull-down resistor may be activated depending on GPIO_PxCFGH/L and

GPIO_PxOUT.



The Schmitt trigger input is connected to the pin.



Reading GPIO_PxIN returns the input at the pin.



The input is also available to on-chip peripherals.

7.6.3. Output Mode

Output mode provides a general purpose output under direct software control. Regardless of whether an output is

configured as push-pull or open-drain, the GPIO’s bit in the GPIO_PxOUT register controls the output. The

GPIO_PxSET and GPIO_PxCLR registers can atomically set and clear bits within GPIO_PxOUT register. These

set and clear registers simplify software using the output port because they eliminate the need to disable interrupts

to perform an atomic read-modify-write operation of GPIO_PxOUT.

When configured in output mode:



The output drivers are enabled and are controlled by the value written to GPIO_PxOUT:



In open-drain mode: 0 activates the N-MOS current sink; 1 tri-states the pin.



In push-pull mode: 0 activates the N-MOS current sink; 1 activates the P-MOS current source.



The internal pull-up and pull-down resistors are disabled.



The Schmitt trigger input is connected to the pin.



Reading GPIO_PxIN returns the input at the pin.

Note: Reading GPIO_PxOUT returns the last value written to the register.

Depending on configuration and usage, GPIO_PxOUT and GPIO_PxIN may not have the same value.

EM341-RTR 数据表(PDF) 51 Page - Silicon Laboratories

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