ST7FDALI View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
ST7FDALI
STMicroelectronics
'ST7FDALI' PDF : 141 Pages View PDF
ST7DALI
7.5 RESET SEQUENCE MANAGER (RSM)
7.5.1 Introduction
The reset sequence manager includes three RE-
SET sources as shown in Figure 14:
■ External RESET source pulse
■ Internal LVD RESET (Low Voltage Detection)
■ Internal WATCHDOG RESET
These sources act on the RESET pin and it is al-
ways kept low during the delay phase.
The RESET service routine vector is fixed at ad-
dresses FFFEh-FFFFh in the ST7 memory map.
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
below)
■ RESET vector fetch
The 256 or 4096 CPU clock cycle delay allows the
oscillator to stabilise and ensures that recovery
has taken place from the Reset state. The shorter
or longer clock cycle delay is automatically select-
ed depending on the clock source chosen by op-
tion byte:
Clock Source
Internal RC Oscillator
External clock (connected to CLKIN pin)
External Crystal/Ceramic Oscillator
(connected to OSC1/OSC2 pins)
CPU clock
cycle delay
256
256
4096
Figure 14. Reset Block Diagram
The RESET vector fetch phase duration is 2 clock
cycles.
If the PLL is enabled by option byte, it outputs the
clock after an additional delay of tSTARTUP (see
Figure 11).
Figure 13. RESET Sequence Phases
Active Phase
RESET
INTERNAL RESET
256 or 4096 CLOCK CYCLES
FETCH
VECTOR
7.5.2 Asynchronous External RESET pin
The RESET pin is both an input and an open-drain
output with integrated RON weak pull-up resistor.
This pull-up has no fixed value but varies in ac-
cordance with the input voltage. It can be pulled
low by external circuitry to reset the device. See
Electrical Characteristic section for more details.
A RESET signal originating from an external
source must have a duration of at least th(RSTL)in in
order to be recognized (see Figure 15). This de-
tection is asynchronous and therefore the MCU
can enter reset state even in HALT mode.
VDD
RESET
RON
Filter
INTERNAL
RESET
PULSE
GENERATOR
WATCHDOG RESET
LVD RESET
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