Operation; Operation As Watch Timer - NEC V850/SA1 mPD703015 Preliminary User's Manual

Figure 8-2. Format of Watch Timer Mode Control Register (WTM) (2/2)
WTM0
0
1
Remarks 1. f : Watch timer clock frequency (f
W
2. ( ) : f

8.4 Operation

8.4.1 Operation as watch timer

The watch timer operates with time intervals of 0.5 seconds with the subsystem clock (32.768 kHz).
The watch timer generates an interrupt request at fixed time intervals.
The count operation of the watch timer is started when bits 0 (WTM0) and 1 (WTM1) of the watch timer mode
control register (WTM) are set to 1. When these bits are cleared to 0, the 5-bit counter is cleared, and the watch
timer stops the count operation.
When the interval timer function is started at the same time, the watch timer can be started from 0 second by
resetting WTM1 to 0. However, an error of up to f
second start for the watch timer because the 9-bit pre-scaler is not cleared.
198
CHAPTER 8
Enables Operation of Watch Timer
Stops operation (clears both prescaler and timer).
Enables operation.
= 32.768 kHz
W
or 2
W
WATCH TIMER
8
/2 or f )
X XT
× 1/f
9
may occur at the first overflow (INTWT) from the 0
W