NEC CHAPTER 10 WATCH TIMER

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CHAPTER 10 WATCH TIMER
(2) Watch timer mode control register (TMC2)
This register sets the watch timer operating mode, watch flag set time and prescaler interval time and enables/
disables prescaler and 5-bit counter operations. TMC2 is set with a 1-bit or 8-bit memory manipulation
instruction.
RESET input sets TMC2 to 00H.
Figure 10-3. Watch Timer Mode Control Register Format
Caution When the watch timer is used, the prescaler should not be cleared frequently.
Remarks 1. fW: Watch timer clock frequency (fXX/27 or fXT)
2. fXX : Main system clock frequency (fX or fX/2)
3. fX: Main system clock oscillation frequency
4. fXT : Subsystem clock oscillation frequency
0
7
TMC26
6
TMC25TMC24
4
TMC23
3210
FF4AH
Address
TMC2
Symbol
TMC22TMC21 TMC20
5
00H
After
Reset
R/W
R/W
0
1
TMC23
fXX = 5.0 MHz Operation
214/fW (0.4 sec)
213/fW (0.2 sec)
Watch Flag Set Time Selection
0
0
0
0
1
1
Other than above
0
0
1
1
0
0
0
1
0
1
0
1
TMC26TMC25 TMC24
fXX = 5.0 MHz Operation
24/fW (410 s)
25/fW (819 s)
26/fW (1.64 ms)
27/fW (3.28 ms)
28/fW (6.55 ms)
29/fW (13.1 ms)
Setting prohibited
fXX = 4.19 MHz Operation
24/fW (488 s)
25/fW (977 s)
26/fW (1.95 ms)
27/fW (3.91 ms)
28/fW (7.81 ms)
29/fW (15.6 ms)
fXT = 32.768 kHz Operation
24/fW (488 s)
25/fW (977 s)
26/fW (1.95 ms)
27/fW (3.91 ms)
28/fW (7.81 ms)
29/fW (15.6 ms)
Prescaler Interval Time Selection
µ
µ
µ
µ
µ
µ
fXX = 4.19 MHz Operation
214/fW (0.5 sec)
213/fW (0.25 sec)
fXT = 32.768 kHz Operation
214/fW (0.5 sec)
213/fW (0.25 sec)
TMC22
0
1
5-Bit Counter Operation Control
Clear after operation stop
Operation enable
TMC21
0
1
Prescaler Operation Control
Clear after operation stop
Operation enable
TMC20
0
1
Watch Operating Mode Selection
Normal operating mode (flag set at fW/214)
Fast feed operating mode (flag set at fW/25)