CHAPTER 7 8-BIT TIMER/EVENT COUNTERS 50 AND 51
User’s Manual U16899EJ2V0UD
185
Figure 7-6. Format of Timer Clock Selection Register 51 (TCL51)
Address: FF8CH After reset: 00H R/W
Symbol
7 6 5 4 3 2 1 0
TCL51 0 0 0 0 0
TCL512
TCL511
TCL510
TCL512 TCL511 TCL510
Count
clock
selection
Note
0
0
0
TI51 falling edge
0
0
1
TI51 rising edge
0 1 0
f
X
(10 MHz)
0 1 1
f
X
/2 (5 MHz)
1 0 0
f
X
/2
4
(625 kHz)
1 0 1
f
X
/2
6
(156.25 kHz)
1 1 0
f
X
/2
8
(39.06 kHz)
1 1 1
f
X
/2
12
(2.44 kHz)
Note Be sure to set the count clock so that the following condition is satisfied.
•
V
DD
= 4.0 to 5.5 V: Count clock
≤
10 MHz
•
V
DD
= 3.3 to 4.0 V: Count clock
≤
8.38 MHz
•
V
DD
= 2.7 to 3.3 V: Count clock
≤
5 MHz
•
V
DD
= 2.5 to 2.7 V: Count clock
≤
2.5 MHz
Cautions 1. When the Ring-OSC clock is selected as the clock to be supplied to the CPU, the clock of the
Ring-OSC oscillator is divided and supplied as the count clock. If the count clock is the Ring-
OSC clock, the operation of 8-bit timer/event counter 51 is not guaranteed.
2. When rewriting TCL51 to other data, stop the timer operation beforehand.
3. Be sure to clear bits 3 to 7 to 0.
Remarks 1. f
X
: High-speed system clock oscillation frequency
2. Figures in parentheses apply to operation at f
X
= 10 MHz.