4 iniTial ReSeT
S1C63003/004/008/016 TeChniCal Manual
Seiko epson Corporation
4-1
(Rev. 1.1)
Initial Reset
4
initial Reset Circuit
4.1
The S1C63003/004/008/016 should be reset to initialize the internal circuits. There are two ways of doing this.
(1) External initial reset by the RESET terminal
(2) External initial reset by simultaneous high input to P00–P03 ports (mask option)
The circuits are initialized by either (1) or (2). When the power is turned on, be sure to initialize using the reset func-
tion. It is not guaranteed that the circuits are initialized by only turning the power on.
Figure 4.1.1 shows the configuration of the initial reset circuit.
RESET
P00
P01
P02
P03
OSC2
OSC1
R
Q
S
Internal
initial
reset
Divider
1 kHz
1 Hz
16 Hz
OSC1
oscillation
circuit
Noise
reject
circuit
Time
authorize
circuit
Mask option
Mask option
V
SS
1.1 Configuration of initial reset circuit
Figure 4.
Reset Terminal (ReSeT)
4.2
Initial reset can be executed externally by setting the reset terminal to a high level (V
DD
). After that the initial reset
is released by setting the reset terminal to a low level (V
SS
) and the CPU starts operating. The reset input signal is
maintained by the RS latch and becomes the internal initial reset signal. The RS latch is designed to be released by
a 16 Hz signal (high) that is divided by the OSC1 clock. Therefore in normal operation, a maximum of 1,024/f
OSC1
seconds (32 msec when f
OSC1
= 32.768 kHz) is needed until the internal initial reset is released after the reset terminal
goes to low level. Be sure to maintain a reset input of 0.1 msec or more. However, when turning the power on, the
reset terminal should be set at a high level as in the timing shown in Figure 4.2.1.
Note that a reset pulse shorter than 100 nsec is rejected as noise.
V
DD
RESET
2.0 msec or more
1.1 V
0.5•V
DD
0.9•V
DD
or more (high level)
Power on
2.1 Initial reset at power on
Figure 4.
The reset terminal should be set to 0.9•V
DD
or more (high level) until the supply voltage becomes 1.1 V or more.
After that, a level of 0.5•V
DD
or more should be maintained more than 2.0 msec.
The reset terminal incorporates a pull-down resistor and a mask option is provided to select whether the resistor is
used or not.