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CMS80F731x Reference Manual
3.
Reset
Reset Time refers to the time from the time the chip resets to the time when the chip starts executing instructions, and its
default design value is about 16ms. This time includes oscillator start time, configuration time. This reset time will exist whether
the chip is powered on reset or otherwise caused by a reset. In addition, when the oscillator is selected as an external low-speed
crystal oscillation (32.768KHz), the reset time (including the oscillation time) is about 1.5s (external capacitor 10pF~22pF) by
default.
The chip can be reset in the following ways:
◆
Power-on reset;
◆
External reset;
◆
Low voltage reset;
◆
Watchdog overflow reset under normal operation;
◆
Internal CONFIG status protection reset.
When any of the above resets occur, all system registers will return to their default state, the program will stop running, the
program counter PC will be cleared to zero, and the program will run from the reset vector 0000H after the reset is completed.
Any kind of reset situation requires a certain response time, and the system provides a perfect reset process to ensure the
smooth progress of the reset operation.
3.1
Power-on Reset
Power-on reset is closely related to LVR operation. The process of powering up the system takes a gradually rising curve
and takes some time to reach the normal level. The normal timing of the power-on reset is given below:
-
Power-up: the system detects that the supply voltage is rising and waits for it to stabilize;
-
System initialization: all system registers are set to initial values;
-
The oscillator begins to work: the oscillator begins to provide the system clock;
-
Execute the program: The power-up ends and the program starts running.
Stabilization Time defaults to 16ms, but if the configuration selects a 32.768KHz crystal oscillator, the settling time is about
1.5s. The power-on reset timing diagram is shown in the following figure:
~~
8ms
configuration
effective
~~
~~
~~
CPU WORK
POR TIME = 16ms
V
LVR
= 1.8 V
VDD
nPOR
(Internal Signal)
RESETB
(Internal Signal)
Oscillation
(CLK)