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CHAPTER 8 TIMER/COUNTER FUNCTION
266
User’s Manual U15109EJ3V0UD
(5) Prescaler mode registers 10, 11, 70, 71 (PRM10, PRM11, PRM70, PRM71)
PRM1n selects the count clock of the 16-bit timer (TM1, TM7) and the valid edge of the TIn0 and TIn1 inputs.
PRMn0 and PRMn1 are set by an 8-bit memory manipulation instruction (n = 1, 7).
RESET input clears PRMn0 and PRMn1 to 00H.
After reset: 00H R/W
Address: FFFFF21EH, FFFFF3AEH
7
6
5
4
3
2
1
0
PRMn1
0
0
0
0
0
0
0
PRMn2
(n = 1, 7)
After reset: 00H R/W
Address: FFFFF216H, FFFFF3A6H
7
6
5
4
3
2
1
0
PRMn0
ESn11
ESn10
ESn01
ESn00
0
0
PRMn1
PRMn0
(n = 1, 7)
ESn11
ESn10
Selects valid edge of TIn1
0
0
Falling edge
0
1
Rising edge
1
0
Setting prohibited
1
1
Both rising and falling edges
ESn01
ESn00
Selects valid edge of TIn0
0
0
Falling edge
0
1
Rising edge
1
0
Setting prohibited
1
1
Both rising and falling edges
Count clock selection
f
PRMn2
PRMn1
PRMn0
Count clock
20 MHz
18.87 MHz
16 MHz
0
0
0
f
/2
100 ns
105 ns
125 ns
0
0
1
f
/4
200 ns
212 ns
250 ns
0
1
0
f
/16
800 ns
848 ns
1
µ
s
0
1
1
TIn0 valid edge
490
−
−
−
1
0
0
f
/32
1.6
µ
s
1.7
µ
s
2
µ
s
1
0
1
f
/128
6.4
µ
s
6.8
µ
s
8
µ
s
1
1
0
f
/256
12.8
µ
s
13.6
µ
s
16
µ
s
1
1
1
Setting prohibited
−
−
−
Note
A pulse longer than twice the internal clock (f
/2) is required for an external clock.