MITSUBISHI MICROCOMPUTERS
3822 Group
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
RESET CIRCUIT
Power on
To reset the microcomputer, RESET pin should be held at an “L”
level for 2 µs or more. Then the RESET pin is returned to an “H”
level (the power source voltage should be between VCC(min.) and
5.5 V, and the quartz-crystal oscillator should be stable), reset is
released. After the reset is completed, the program starts from the
address contained in address FFFD16 (high-order byte) and ad-
dress FFFC16 (low-order byte). Make sure that the reset input
voltage meets VIL spec. when a power source voltage passes
VCC(min.).
Power
source
voltage
RESET
VCC
0V
Reset input
voltage
V
IL spec.
0V
RESET
VCC
Power source voltage
detection circuit
Fig. 39 Reset Circuit Example
XIN
φ
RESET
Internal
reset
Reset address from
vector table
Address
?
?
?
?
FFFC
FFFD
ADH, ADL
Data
ADL
ADH
SYNC
XIN : about 8000 cycles
Notes 1: The frequency relation of f(XIN) and f(φ) is f(XIN) =8•f(φ)
2: The question marks (?) indicate an undefined state that depends on the previous state.
Fig. 40 Reset Sequence
41
MITSUBISHI [ Mitsubishi Group ]
