m3819 Renesas Electronics Corporation., m3819 Datasheet - Page 177

• Manufacturer Part Number: m3819
• Description: Mitsubishi 8-bit Single-chip Microcomputer 740 Family / 38000 Series
• Manufacturer: Renesas Electronics Corporation.

2. APPLICATION
Fig. 2.9.15 Timing chart of counting without clock errors during a power failure
(2) Counting without clock error during a power
Figure 2.9.15 shows a timing chart of counting without clock errors during a power failure, Figure 2.9.16 shows a
structure of a clock counter, and Figures 2.9.17 and 2.9.18 show a setting of related registers.
failure
Outline : It keeps counting without clock errors
Specifications :
• Keep a power consumption as low as possible
• Keep counting a clock correctly.
• f(X
• The Timer 1 interrupt is used in a normal power state.
• Port processing
while maintaining a clock function.
The Timer 3 interrupt is used during a power failure.
Input port : Fix to “H” or “L” level in the external
Output port : Fix to an output level which does not
I/O port : Input port — Fix to “H” or “L” level in the external unit.
V
P4
REF
5
IN
Internal system
clock
/ZCR (using as the input port) : Fix to “H” level in the external unit.
) = 4.19 MHz, f(X
: Supplying to the Reference voltage input pin is stopped by the external circuit.
during a power failure.
Output port — Output the data which does not consume current.
unit.
cause a current flow to the external
unit.
[Example]
When a circuit turns on LED at “L” output level, fix the output level to “H”.
X
Release reset
X
CIN
IN
Selection of X
oscillating function
CIN
f(X
) = 32.768 kHz
IN
)/8
Change the internal
system clock to f(X
(high-speed mode).
CIN
3819 Group USER’S MANUAL
Detection of power failure
f(X
IN
IN
)/2
)/2
Fig. 2.9.14 Connection diagram [Counting without
2.9 Clock generating circuit
3819 group
Input port
After detecting a power
failure, change the internal
system clock to f(X
stop operating of f(X
Note :
(Note)
clock errors during a power failure]
Signal is detected by inputting
to each input port, interrupt
input pin, and analog input pin.
f(X
CIN
MITSUBISHI MICROCOMPUTER
)/2
Power failure detection signal
CIN
IN
) and
).
3819 Group
163