UPD6600A NEC, UPD6600A Datasheet - Page 16

• Manufacturer Part Number: UPD6600A
• Description: 4-BIT SINGLE-CHIP MICROCONTROLLER FOR REMOTE CONTROL TRANSMISSION
• Manufacturer: NEC

16
15. AC PIN (ALL CLEAR PIN)
WATCHDOG TIMER FUNCTION
by connecting a 0.1 F capacitor across the AC pin and the V
Caution
Internal part of the CPU including the program counter can be reset by setting the AC pin to the low level.
A power-on reset function and a CR watchdog timer function, that can be controlled by program, can be realized
Charge mode
Charge-discharge
pattern
Discharge mode
When the watchdog timer function is not used, switch to charging mode by executing a NOP
instruction immediately before a HALT instruction at the beginning of the program. (Be sure to
connect the capacitor.)
0.1 F
0.1 F
V
V
thL
DD
V
V
DD
Charge start instruction
Discharge start instruction
Execute HALT instruction
immediately before NOP.
(Charge for 0.4 ms or more)
Discharge starts after the NOP
instruction execution.
(Discharge time is about 5 ms from V
SS
.
t
The pattern must be
controlled by the program,
in such a manner that
the C charge level will not
go below V
PD6124A, 6600A
thL
DD
.
to V
thL
)