Operation In The Interval Timer Mode; Operation In The Standby Mode - Hitachi SH7095 Hardware User Manual

12.3.2

Operation in the Interval Timer Mode

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).
ITI: Interval timer interrupt request generation
12.3.3

Operation in the Standby Mode

The watchdog timer has a special function to clear the standby mode with an NMI interrupt. When
using the standby mode, set the WDT as described below.
Transition to the Standby Mode: The TME bit in the WTCSR must be cleared to 0 to stop the
watchdog timer counter before it enters the standby mode. The chip cannot enter the standby mode
while the TME bit is set to 1. Set bits CKS2 to CKS0 so that the counter overflow interval is equal
to or longer than the oscillation settling time. See section15, Electrical Characteristics, for the
oscillation settling time.
Recovery from the 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 to CKS0 before the standby mode was entered. When the WTCNT overflows (changes
from H'FF to H'00) the system clock (φ) is presumed to be stable and usable; clock signals are
supplied to the entire chip and the standby mode ends.
For details on the standby mode, see section 2.5.2, Power Down States.
318 Hitachi
Figure 12.5 Operation in the Interval Timer Mode