HA16117FPA RENESAS [Renesas Technology Corp], HA16117FPA Datasheet - Page 6

• Manufacturer Part Number: HA16117FPA
• Description: CMOS Watchdog Timer
• Manufacturer: RENESAS [Renesas Technology Corp]

HA16117F Series
Timing Waveforms and Functional Description
Watchdog On/Off Function
A feature of the HA16117F is that watchdog supervision can be switched on and off. When the watchdog function is
switched on, both the supply voltage and
P-RUN input are monitored to detect abnormal conditions. When the watchdog function is switched off (standby
mode), only the supply voltage is monitored. Watchdog supervision is switched on and off by the input at the ACC pin
(pin 7): Supervision is on when ACC is low, and off when ACC is high.
Many MPUs have a standby mode in which the CPU stops running but memory contents are retained. In standby mode,
program execution halts and I/O ports go to the high-impedance state, so there is no need for the watchdog timer to
supervise pulse output from an I/O port to detect abnormal conditions. Power can be saved by placing both the MPU
and HA16117F in standby mode at the same time. The HA16117F is designed to draw a typical standby current I
of only 43 A Typ when the watchdog function is switched off.
ACC Pin (pin 7) and RES Output
When the MPU returns from standby mode to normal operation it generally takes 10 to 200 ms for the clock oscillator
in the MPU to stabilize. The RES signal is not output during this setup time. After the setup time (t
RES is output if the P-RUN signal from the MPU is still abnormal.
Rev.3.00 Jun 15, 2005 page 6 of 30
Watchdog function on
Watchdog function off
ACC pin
RES (due to MPU crash)
(V
(V
ACC
ACC
V
P-RUN
RES
RES
= "High")
CC
= "Low")
Figure 2 ACC Pin and RES Output
Figure 1 Timing Waveforms
t
t
ON
ON
t
OFF
Crash
t
RL
t
RH
t
SH
V
TL
t
SL
t
t
ON
ON
Adjust according to
MPU's setup time
SL
) has elapsed,
STBY