Fujitsu MB90460 Series, Hardware Manual, Page: 476 / 739

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CHAPTER 16 PWC Timer
●
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
µ
s 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.
■
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
T
W
= n x t / Div (
µ
s)
T
W
Measured pulse width or pulse period (
µ
s)
......
n
Measurement result contained in PWC0/PWC1
......
t
Count clock period (
µ
s)
......
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)
Table 16.6-5 Pulse Width Measurement Range
Division rate
DIV1,
DIV0
CKS1,CKS0=00
B
(
φ
/4) CKS1,CKS0=01
B
(
φ
/16) CKS1,CKS0=10
B
(
φ
/32)
No division - 0.125
µ
s to 16.38 ms [0.25
µ
s] 0.125
µ
s to 65.5 ms [1.0
µ
s] 0.125
µ
s to 131 ms [2
µ
s]
Divide-by 4
00
B
0.125
µ
s to 4.10 ms [62.5 ns] 0.125
µ
s to 16.38 ms [0.25
µ
s] 0.125
µ
s to 32.75 ms [500 ns]
Divide-by 16
01
B
0.125
µ
s to 1024
µ
s [15.6 ns] 0.125
µ
s to 4.10 ms [62.5 ns] 0.125
µ
s to 8.19 ms [125 ns]
Divide-by 64
00
B
0.125
µ
s to 256
µ
s [3.91 ns] 0.125
µ
s to 1024
µ
s [15.6 ns] 0.125
µ
s to 2.048 ms [31.25 ns]
Divide-by 256
11
B
0.125
µ
s to 64
µ
s [0.98 ns] 0.125
µ
s to 256
µ
s [3.91 ns] 0.125
µ
s to 512
µ
s [7.81 ns]
(Note) The number in [ ] indicates the resolution per bit.