CMS32L051 User Manual |Chapter 22 Power-On Reset Circuit
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Chapter 22 Power-On Reset Circuit
22.1 Function of power-on reset circuit
The power-on reset circuit (POL) has the following functions.
Internal reset signal is generated when power is turned on.
If the supply voltage (V
DD
) exceeds the sense voltage (V
POL
), the reset is released. However, the reset
state must be maintained by voltage detection circuitry or an external reset before the supply voltage reaches
the operating voltage range shown in the AC characteristics of the data sheet.
Drag the supply voltage (V
DD
) and the detection voltage (V
PDR
) to compare. While V
DD
＜V
PDR
, an
internal reset signal is generated. However, when the supply voltage drops, the supply voltage must be lower
than AC characteristics of the data sheet before the operating voltage range shown. It is reset by means of
transfer in deep sleep mode, voltage detection circuitry, or external reset. When restarting operation, you must
confirm that the supply voltage has returned to the operating voltage range.
Note that when the power-on reset circuit generates an internal reset signal, clear the reset control flag register (RESF) to
00H.
Note 1 The CMS32L051 contains several hardware that generates an internal reset signal. Flags used to indicate the
reset source are assigned when an internal reset signal is generated by the access of a watchdog timer (WDT),
voltage detection (LVD) circuit, system reset request position bit, RAM parity error, or illegal memory RESF
registers; When an internal reset signal is generated by WDT, LVD, assertion of the system reset request bit, RAM
parity error, or access to illegal memory, the RESF register is not cleared to 00H Set the flag to 1. For more
information on RESF registers, refer to Chapter 21 Reset Functions.
2.V
POR
: POR supply voltage rise detection voltage
V
PDR
: POR supply voltage drop detection voltage
For details, please refer to the POR circuit characteristics in the data sheet.
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