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2 POWER SUPPLY, RESET, AND CLOCKS
2.2.2 Input Pin
Table 2.2.2.1 shows the SRC input pin.
Pin name
#RESET
The #RESET pin is connected to the noise filter that removes pulses not conforming to the requirements. The #RE-
SET pin includes a pull-up resistor that can be enabled/disabled using the SRCRESETPCTL.PORT_PLUP_EN bit.
For the #RESET pin characteristics, refer to "#RESET pin characteristics" in the "Electrical Characteristics" chapter.
2.2.3 Reset Sources
The reset source refers to causes that request system initialization. The following shows the reset sources.
#RESET pin
Inputting a reset signal with a certain low level period to the #RESET pin issues a reset request.
POR and BOR
POR (Power On Reset) issues a reset request when the rise of V
a reset request when a certain V
system will be reset properly when the power is turned on and the supply voltage is out of the operating volt-
age range. Figure 2.2.3.1 shows an example of POR and BOR internal reset operation according to variations in
V
.
DD
V
DD
V
SS
Internal state
X
RST
V
: Reset detection voltage V
RST-
For the POR and BOR electrical specifications, refer to "POR/BOR characteristics" in the "Electrical Charac-
teristics" chapter.
Reset request from the CPU
The CPU issues a reset request by writing 1 to the AIRCR.SYSRESETREQ bit in the Cortex
plication Interrupt and Reset Control Register. For more information, refer to the "ARM
Reference Manual."
Key-entry reset
Inputting a low level signal of a certain period to the I/O port pins configured to a reset input issues a reset re-
quest. This function must be enabled using an I/O port register. For more information, refer to the "I/O Ports"
chapter.
Watchdog timer reset
Setting the watchdog timer into reset mode will issue a reset request when the counter overflows. This helps re-
turn the runaway CPU to a normal operating state. For more information, refer to the "Watchdog timer" chapter.
Supply voltage detector reset
By enabling the low power supply voltage detection reset function, the supply voltage detector will issue a reset
request when a drop in the power supply voltage is detected. This makes it possible to put the system into reset
state if the IC must be stopped under a low voltage condition. For more information, refer to the "Supply Volt-
age Detector" chapter.
2-4
Table 2.2.2.1 SRC Pin
I/O
Initial status
I
I (Pull-up)
voltage level is detected. Reset requests from these circuits ensure that the
DD
V
RST+
V
V
RST-
RST-
RUN
RST
Reset canceling voltage
RST+:
Figure 2.2.3.1 Example of Internal Reset by POR and BOR
Seiko Epson Corporation
Reset input
is detected. BOR (Brownout Reset) issues
DD
V
RST-
RUN
RST
X
X
Indefinite (operating limit)
RST
Function
V
RST+
RST
RUN
RESET state
RUN
CPU RUN state
-M0+ Ap-
®
v6-M Architecture
®
S1C31W65 TECHNICAL MANUAL
(Rev. 1.1)
X
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