
185
CHAPTER 7 APPLICATIONS OF WATCH TIMER
Figure 7-4. Format of Watch Timer Mode Control Register
(
μ
PD78054, 78054Y, 78064, 78064Y, 78078, 78078Y, 780018, 780018Y, 780058,
780058Y, 780308, 780308Y, 78058F, 78058FY, 78064B, 78075B, 78075BY
subseries,
μ
PD78070A, 78070AY)
TMC20
Selects watch operation mode
0
Normal operation mode (sets flag at f
W
/2
14
)
1
Fast-forward mode (sets flag at f
W
/2
5
)
TMC21
Controls operation of prescaler
0
Clears after operation stopped
1
Enables operation
TMC22
Controls operation of 5-bit counter
0
Clears after operation stopped
1
Enables operation
TMC23
Selects set time of watch timer
At f
XX
= 5.0 MHz
At f
XX
= 4.19 MHz
At f
XT
= 32.768 kHz
0
2
14
/f
W
(0.4 sec)
2
14
/f
W
(0.5 sec)
2
14
/f
W
(0.5 sec)
1
2
13
/f
W
(0.2 sec)
2
13
/f
W
(0.25 sec)
2
13
/f
W
(0.25 sec)
TMC26 TMC25 TMC24
Selects interval time of prescaler
At f
XX
= 5.0 MHz
At f
XX
= 4.19 MHz
At f
XT
= 32.768 kHz
0
0
0
2
4
/f
W
(410
μ
s)
2
4
/f
W
(488
μ
s)
2
4
/f
W
(488
μ
s)
0
0
1
2
5
/f
W
(819
μ
s)
2
5
/f
W
(977
μ
s)
2
5
/f
W
(977
μ
s)
0
1
0
2
6
/f
W
(1.64 ms)
2
6
/f
W
(1.95 ms)
2
6
/f
W
(1.95 ms)
0
1
1
2
7
/f
W
(3.28 ms)
2
7
/f
W
(3.91 ms)
2
7
/f
W
(3.91 ms)
1
0
0
2
8
/f
W
(6.55 ms)
2
8
/f
W
(7.81 ms)
2
8
/f
W
(7.81 ms)
1
0
1
2
9
/f
W
(13.1 ms)
2
9
/f
W
(15.6 ms)
2
9
/f
W
(15.6 ms)
Others
Setting prohibited
Caution Do not often clear the prescaler when the watch timer is used.
Remarks 1.
f
W
: watch timer clock frequency (f
XX
/2
7
or f
XT
)
2.
f
XX
: main system clock frequency (f
X
or f
X
/2)
3.
f
X
: main system clock oscillation frequency
4.
f
XT
: subsystem clock oscillation frequency
7
6
5
4
3
2
Symbol
1
0
FF4AH
TMC20
TMC2
TMC21
TMC23 TMC22
TMC24
TMC25
TMC26
0
Address
At reset
R/W
00H
R/W