Watch Timer Operations; Watch Timer Operation; Interval Timer Operation; Interval Timer Interval Time - NEC PD78052 User Manual

10.4 Watch Timer Operations

10.4.1 Watch timer operation

When the 32.768-kHz subsystem clock or 4.19-MHz main system clock is used, the timer operates as a watch
timer with a 0.5-second or 0.25-second interval.
The watch timer sets the test input flag (WTIF) to 1 at the constant time interval. The standby state (STOP mode/
HALT mode) can be cleared by setting WTIF to 1.
When bit 2 (TMC22) of the watch timer mode control register (TMC2) is set to 0, the 5-bit counter is cleared and
the count operation stops.
For simultaneous operation of the interval timer, zero-second start can be achieved by setting TMC22 to 0
(maximum error: 26.2 ms when operated at f

10.4.2 Interval timer operation

The watch timer operates as interval timer which generates interrupt requests repeatedly at an interval of the preset
count value.
The interval time can be selected with bits 4 to 6 (TMC24 to TMC26) of the watch timer mode control register.
TMC26 TMC25 TMC24
0 0 0
0 0 1
0 1 0
0 1 1
1 0 0
1 0 1
Other than above
Remark f : Main system clock frequency (f
XX
f : Main system clock oscillation frequency
X
f : Subsystem clock oscillation frequency
XT
f : Watch timer clock frequency (f
W
246
CHAPTER 10 WATCH TIMER
= 5.0 MHz).
XX
Table 10-3. Interval Timer Interval Time
When operated at
Interval Time
f
XX
4
2 1/f
W
5
2 1/f
W
6
2 1/f
W
7
2 1/f
W
8
2 1/f
W
9
2 1/f
W
Setting prohibited
When operated at
= 5.0 MHz f = 4.19 MHz
XX
410 s 488 s
819 s 977 s
1.64 ms 1.95 ms
3.28 ms 3.91 ms
6.55 ms 7.81 ms
13.1 ms 15.6 ms
or f /2)
X X
7
/2 or f )
XX XT
When operated at
f = 32.768 kHz
XT
488 s
977 s
1.95 ms
3.91 ms
7.81 ms
15.6 ms