Fujitsu MB90460 Series Hardware Manual page 476

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Continuous measurement mode
At termination of measurement, the timer measurement results are transferred to PWC0/ PWC1.
When PWC0/ PWC1 is read, the previous measurement results are read. While measurement is in
progress, the previous measurement results are stored in PWC0/ PWC1. During measurement, the timer
value cannot be read.
In continuous measurement mode, unless the previous measurement results are read before completion of
the next measurement, a new measurement result overwrites the existing value. The error flag (ERR) of
PWCSH0/PWCSH1 is set. When PWC0/ PWC1 is read, the error flag (ERR) is cleared automatically.
■ Minimum Input Pulse Width
The pulse must be input to the pulse-width count input pin (PWI0/PWI1) longer than the following
minimum input pulse width.
Pulse width: 2 machine cycles (0.125 µs or more for the machine clock at 16 MHz)
However, the input pulse that is shorter than the above specification may also be recognized as a valid
pulse.
■ Calculating Pulse Width/period
The pulse width or pulse period of the measurement object is calculated based on the count result read from
PWC0/PWC1 at the end of a count as follows.
T = n x t / Div (µs)
W
■ Pulse Width/period Measurement Range
The range of the pulse width/period that can be measured depends on the count clock and division rate of
an input divider.
Table 16.6-5 lists the measurement range for the machine cycle (indicated by φ) at 16 MHz
Table 16.6-5 Pulse Width Measurement Range
DIV1,
Division rate
DIV0
No division -
00
Divide-by 4
B
01
Divide-by 16
B
00
Divide-by 64
B
11
Divide-by 256
B
(Note) The number in [ ] indicates the resolution per bit.
......
T
Measured pulse width or pulse period (µs)
W
......
n
Measurement result contained in PWC0/PWC1
......
t Count clock period (µs)
......
Div Division rate set in the division rate register (DIV0/DIV1)
(a value of "1" is used in a mode other than the division count mode)
CKS1,CKS0=00 (φ/4)
B
0.125 µs to 16.38 ms [0.25 µs] 0.125 µs to 65.5 ms [1.0 µs]
0.125 µs to 4.10 ms [62.5 ns]
0.125 µs to 1024 µs [15.6 ns]
0.125 µs to 256 µs [3.91 ns]
0.125 µs to 64 µs [0.98 ns]
CKS1,CKS0=01 (φ/16)
B
0.125 µs to 16.38 ms [0.25 µs] 0.125 µs to 32.75 ms [500 ns]
0.125 µs to 4.10 ms [62.5 ns]
0.125 µs to 1024 µs [15.6 ns]
0.125 µs to 256 µs [3.91 ns]
CHAPTER 16 PWC Timer
CKS1,CKS0=10 (φ/32)
B
0.125 µs to 131 ms [2 µs]
0.125 µs to 8.19 ms [125 ns]
0.125 µs to 2.048 ms [31.25 ns]
0.125 µs to 512 µs [7.81 ns]
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