2 POWER SUPPLY, RESET, AND CLOCKS
2-4
Seiko epson Corporation
S1C17F13 TeChniCal Manual
(Rev. 1.0)
Internal state
V
RST-
: Reset detection voltage
V
RST+:
Reset canceling voltage
Indefinite (operating limit)
RESET state
CPU RUN state
X
RST
RUN
V
DD
V
SS
V
RST-
V
RST-
V
RST-
V
RST+
V
RST+
X
X
X
RST
RST
RST
RST
RUN
RUN
RUN
2.3.1 Example of Internal Reset by POR and BOR
Figure 2.
For the POR and BOR electrical specifications, refer to “POR/BOR characteristics” in the “Electrical Charac-
teristics” chapter.
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.
Peripheral circuit software reset
Some peripheral circuits provide a control bit for software reset (MODEN or SFTRST). Setting this bit initial-
izes the peripheral circuit control bits. Note, however, that the software reset operations depend on the periph-
eral circuit. For more information, refer to “Control Registers” in each peripheral circuit chapter.
Note: The MODEN bit of some peripheral circuits does not issue software reset.
Initialization Conditions (Reset Groups)
2.2.4
A different initialization condition is set for the CPU registers and peripheral circuit control bits, individually. The
reset group refers to an initialization condition. Initialization is performed when a reset source included in a reset
group issues a reset request. Table 2.2.4.1 lists the reset groups. For the reset group to initialize the registers and
control bits, refer to the “CPU and Debugger” chapter or “Control Registers” in each peripheral circuit chapter.
2.4.1 List of Reset Groups
Table 2.
Reset group
Reset source
Reset cancelation timing
H0
#RESET pin
POR and BOR
Supply voltage detector reset
Key-entry reset
Watchdog timer reset
Reset state is maintained for the reset
hold time t
RSTR
after the reset request is
canceled.
H1
#RESET pin
POR and BOR
S0
Peripheral circuit software reset
(MODEN and SFTRST bits. The
software reset operations de-
pend on the peripheral circuit.
Reset state is canceled immediately
after the reset request is canceled.