38K2 Datasheet, PDF (93/151 Pages) Renesas Technology Corp – SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER

38K2 Group
RESET CIRCUIT
To reset the microcomputer, RESET pin should be held at an “L”
level for 16 cycles or more of XIN. Then the RESET pin is returned
to an “H” level (the power source voltage should be between 3.0 V
and 5.25 V for L version, and the oscillation should be stable), re-
set is released. After the reset is completed, the program starts
from the address contained in address FFFD16 (high-order byte)
and address FFFC16 (low-order byte). Make sure that the reset in-
put voltage is under 0.6 V for VCC of 3.0 V (L version).
RESET
Power source
VCC ^voltage
0V
Reset input
voltage
0V
Poweron
(Note)
0.2VCC
Note : Reset release voltage ;
Vcc = 3.0 V (L version)
RESET
VCC
Power source
voltage detection
circuit
Fig. 137 Example of reset circuit
XIN
φ
RESET
Internal
reset
Address
Data
SYNC
?
?
?
?
FFFC FFFD ADH,L
Reset address from the vector table.
?
?
?
?
ADL
ADH
XIN: 10.5 to 18.5 clock 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. 138 Reset sequence
Rev.3.00 Oct 15, 2006 page 93 of 147
REJ03B0193-0300