參數(shù)資料
型號: MC68HC05X4DW
廠商: MOTOROLA INC
元件分類: 微控制器/微處理器
英文描述: HCMOS Microcontroller Unit
中文描述: 8-BIT, MROM, 2.2 MHz, MICROCONTROLLER, PDSO28
封裝: SOIC-28
文件頁數(shù): 48/156頁
文件大?。?/td> 926K
代理商: MC68HC05X4DW
Resets, Interrupts and Low Power Modes
MC68HC05X4
48
Resets, Interrupts and Low Power Modes
For More Information On This Product,
Go to: www.freescale.com
MOTOROLA
Power-on reset
A power-on reset occurs when a positive transition is detected on VDD.
The power-on reset function is strictly for power turn-on conditions and
should not be used to detect drops in the power supply voltage. The
power-on circuitry provides a stabilisation delay (t
PORL
) from when the
oscillator becomes active. If the external RESET pin is low at the end of
this delay then the processor remains in the reset state until RESET
goes high. The user must ensure that the voltage on VDD has risen to a
point where the MCU can operate properly by the time t
PORL
has elapsed.
If there is doubt, the external RESET pin should remain low until the
voltage on VDD has reached the specified minimum operating voltage.
This may be accomplished by connecting an external RC-circuit to this
pin to generate a power-on reset (POR). In this case, the time constant
must be great enough (at least 100 ms) to allow the oscillator circuit to
stabilise.
Figure 1. Power-on reset and RESET
V
DD
RESET
1FFF
1FFE
1FFE
1FFE
New
PC
7FFF
7FFE
7FFE
7FFE
OSC1
New
PC
Internal
address bus
Internal
processor clock
7FFE
Op
code
New
PCL
New
PCH
t
VDDR
Op
code
New
PCL
New
PCH
Internal
data bus
t
OXOV
t
CYC
t
PORL
1FFE
Program
execution
begins
Program
execution
begins
t
RL
(or t
DOGL
)
(Internal power-on reset)
(External hardware reset)
V
DD
threshold (1-2V typical)
Reset sequence
Reset sequence
2-resets
F
Freescale Semiconductor, Inc.
n
.
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