(f) Pulse Width/Period Calculation
Calculate the width or period of the measured pulse from the count result read from PWCR after the
count ends as follows.
T
= n × t ÷ D
w
(g) Pulse Width/Period Count Range
The range of pulse widths/periods that can be measured depends on the count clock and the divide
ratio of the input divider.
The table below lists the measurement range for a 16MHz machine cycle (indicated by φ below).
Divide Ratio
No division
Divide by 4
Divide by 16
Divide by 64
Divide by 256
Note:
The figures in [ ] indicate the resolution per bit.
(h) Generation of Interrupt Requests
The following two interrupt requests can be generated in pulse width count mode.
(1) Timer overflow interrupt request
If an overflow occurs during counting, the overflow flag is set and, if the overflow interrupt request is
enabled, an interrupt request is generated.
(2) Count end interrupt request
When the count end edge is detected, the count end flag (EDIR) in PWCSR is set and, if the count
end interrupt request is enabled, an interrupt request is generated.
The count end flag (EDIR) is automatically cleared by reading PWCR.
MB90580 Series
T
... Measured pulse width or period (µs)
w
n ... Count result stored in PWCR
(µs)
t
... Count clock period (µs)
IV
D
... Divide ratio set in the divide ratio register (DIVR)
IV
(Use the value 1 for modes other than divided period count mode.)
Table 18.4g Pulse Width Count Range
DIV1.0
CKS1, 0 = 00 (φ/4)
–
0.125µs to 16.38ms
[0.25µs]
00
0.125µs to 4.10ms
B
[62.5µs]
01
0.125µs to 1024µs
B
[15.6ns]
10
0.125µs to 256µs
B
[3.91ns]
11
0.125µs to 64µs
B
[0.98ns]
CKS1, 0 = 01 (φ/16)
0.125µs to 65.5ms
[1.6µs]
0.125µs to 16.38ms
[0.4µs]
0.125µs to 4.10ms
[0.1µs]
0.125µs to 1024µs
[25.0ns]
0.125µs to 256µs
[6.25ns]
Chapter 18: Pulse Width Counter (PWC) Timer
18.4 Operations
CKS1, 0 = 10 (φ/32)
0.2µs to 131ms
[3.2µs]
0.2µs to 32.75ms
[800ns]
0.2µs to 8.19ms
[200ns]
0.2µs to 2.048ms
[50.0ns]
0.2µs to 512ms
[12.5ns]
263