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RM0016

Reset (RST)

 

 

8 Reset (RST)

There are 9 reset sources:

External reset through the NRST pin

Power-on reset (POR)

Brown-out Reset (BOR)

Independent watchdog reset (IWDG)

Window watchdog reset (WWDG)

Software reset

SWIM reset

Illegal opcode reset

EMC reset: generated if critical registers are corrupted or badly loaded

These sources act on the RESET pin and it is always kept low during the delay phase. The RESET service routine vector is fixed at address 6000h in the memory map.

Figure 18. Reset circuit

 

 

 

 

 

 

VDD_IO

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

RPU

 

 

 

 

 

 

 

 

 

 

 

 

 

 

EXTERNAL

 

 

 

 

 

 

 

 

 

(typ 45 kΩ)

 

 

 

SYSTEM NRESET

 

 

 

 

 

 

 

 

 

Filter

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

RESET

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

NRST

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

POR/BOR RESET

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

PULSE

 

 

 

 

 

 

IWDG/WWDG/SOFTWARE RESET

 

 

 

 

 

 

 

 

 

 

 

 

 

GENERATOR

 

 

 

 

 

 

 

SWIM RESET

 

 

 

 

 

 

 

 

 

 

 

 

 

(min 20 µs)

 

 

 

 

 

 

ILLEGAL OPCODE RESET

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

EMC RESET

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

8.1“Reset state” and “under reset” definitions

When a reset occurs, there is a reset phase from the external pin pull-down to the internal reset signal release. During this phase, the microcontroller sets some hardware configurations before going to the reset vector.

At the end of this phase, most of the registers are configured with their “reset state” values. During the reset phase, i.e. “under reset”, some pin configurations may be different from their “reset state” configuration.

8.2Reset circuit description

The NRST pin is both an input and an open-drain output with integrated RPU weak pull-up resistor.

The low pulse of duration tINFP(NRST) on the NRST pin generates an external reset. The reset detection is asynchronous and therefore the MCU can enter reset even in Halt mode.

The NRST pin also acts as an open-drain output for resetting external devices.

Doc ID 14587 Rev 9

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