HD6417034B RENESAS [Renesas Technology Corp], HD6417034B Datasheet - Page 374

• Manufacturer Part Number: HD6417034B
• Description: 32-Bit RISC Microcomputer
• Manufacturer: RENESAS [Renesas Technology Corp]

Section 12 Watchdog Timer (WDT)
12.3.2
To use the WDT as an interval timer, clear WT/IT to 0 and set TME to 1. An interval timer
interrupt (ITI) is generated each time the timer counter overflows. This function can be used to
generate interval timer interrupts at regular intervals (figure 12.5).
12.3.3
The watchdog timer has a special function to clear standby mode with an NMI interrupt. When
using standby mode, set the WDT as described below.
Transition to Standby Mode: The TME bit in TCSR must be cleared to 0 to stop the watchdog
timer counter before it enters standby mode. The chip cannot enter standby mode while the TME
bit is set to 1. Set bits CKS2–CKS0 so that the counter overflow interval is equal to or longer than
the oscillation settling time. See sections 20.1.3 and 20.2.3, AC Characteristics, for the oscillation
settling time.
Recovery from Standby Mode: When an NMI request signal is received in standby mode, the
clock oscillator starts running and the watchdog timer starts counting at the rate selected by bits
CKS2–CKS0 before standby mode was entered. When TCNT overflows (changes from H'FF to
H'00), the system clock ( ) is presumed to be stable and usable; clock signals are supplied to the
entire chip and standby mode ends.
For details on standby mode, see section 19, Power Down State.
Rev. 7.00 Jan 31, 2006 page 348 of 658
REJ09B0272-0700
H'FF
H'00
ITI: Interval timer interrupt request
TCNT value
WT/IT = 0
Operation in Interval Timer Mode
Operation in Standby Mode
TME = 1
Figure 12.5 Operation in Interval Timer Mode
Overflow
ITI
Overflow
ITI
Overflow
ITI
Overflow
ITI
Time