ST7FOXK2 datasheet(40/226 Pages) STMICROELECTRONICS

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Supply, reset and clock management

ST7FOXF1, ST7FOXK1, ST7FOXK2

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6.3

Reset sequence manager (RSM)

6.3.1

Introduction

The reset sequence manager includes three RESET sources as shown in Figure 14:

●

External RESET source pulse

●

Internal LVD RESET (Low Voltage Detection)

●

Internal WATCHDOG RESET

Note:

A reset can also be triggered following the detection of an illegal opcode or prebyte code.

Refer to Section 11.2.1 on page 184 for further details.

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 addresses FFFEh-FFFFh in the ST7 memory

mapping.

The basic RESET sequence consists of 3 phases as shown in Figure 13:

●

Active Phase depending on the RESET source

●

256 or 4096 CPU clock cycle delay (see Table 13)

Caution:

When the ST7 is unprogrammed or fully erased, the Flash is blank and the Reset vector is

not programmed. For this reason, it is recommended to keep the RESET pin in low state

until programming mode is entered, in order to avoid unwanted behavior.

The 256 or 4096 CPU clock cycle delay allows the oscillator to stabilize and ensures that

recovery has taken place from the Reset state. The shorter or longer clock cycle delay is

automatically selected depending on the clock source chosen by option byte.

The Reset vector fetch phase duration is 2 clock cycles.

Table 8.

ST7 clock sources

Hardware configuration

OSC1

OSC2

LOAD

CAPACITORS

ST7

CL2

CL1

OSC1

OSC2

ST7

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