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M30245 Group
2.2.13 Precautions for Timer A (event counter mode)
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(1) Down count
Counter value
(Hex.)
Read value
(Hex.)
Figure 2.2.29. Reading timer Ai register
TA2
TA3
TA4
TA2
TA3
TA4
Figure 2.2.30. Standard of 2-phase pulses
Rev.2.00 Oct 16, 2006
REJ09B0340-0200
(1) To clear reset, the count start flag is set to "0". Set a value in the timer Ai register, then set the
flag to "1".
(2) Reading the timer Ai register while a count is in progress allows reading, with arbitrary timing,
the value of the counter. Reading the timer Ai register with the reload timing shown in Figure
2.2.29 gets "FFFF
" by underflow or "0000
16
setting a value in the timer Ai register with a count halted but before the counter starts count-
ing gets a proper value.
(3) Please note the standards for the differences between the 2 pulses used in the two-phase
pulse signals input signals to the TAi
2.2.30.
(4) When free run type is selected, if count is stopped, set a value in the timer Ai register again.
Reload
2
1
0
2
1
0
n = reload register content
T1
IN
IN
IN
OUT
OUT
T2
T3
OUT
page 35 of 354
" by overflow. Reading the timer Ai register after
16
pin and TAi
IN
(2) Up count
Counter value
n
n – 1
(Hex.)
Read value
n – 1
FFFF
(Hex.)
Time
pin (i = 2, 3, 4), as shown in Figure
OUT
Reload
FFFD FFFE FFFF
FFFD FFFE FFFF 0000 n + 1
n = reload register content
Vcc = 5V, f(X
) = 20MHz
IN
T1
T2, T3
(Min.)
(Min.)
800ns
200ns
Vcc = 3V, f(X
) = 10MHz
IN
T1
T2, T3
(Min.)
(Min.)
2µs
500ns
2. Timer A
n
n + 1
Time
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