Fujitsu F2MC-16LX MB90580 Series Hardware Manual page 282

18.4 Operations
Count Mode
Inter-edge pulse
width count
Divided period
count
In all modes, the timer does not count during the time between starting the count and a count start edge
being input. After the count start edge is input, the timer is cleared to 0000
each count clock until a count end edge is input.
The following operations are performed when a count end edge is input.
(1) The count end flag (EDIR) in PWCSR is set.
(2) The timer stops counting (unless the timer is restarted at the same time).
(3) In continuous count mode:The timer value (count result) is transferred to PWCR and the count
remains stopped until the next count start edge is input.
(4) In single-shot count mode:The timer stops counting (unless the timer is restarted at the same time).
In continuous count mode, the end edge also acts as the next start edge in some modes, including
inter-edge pulse width count mode and period count mode.
(e) Minimum Input Pulse Width
Pulses input to the pulse width count input pins (PWC3 to PWC0) must be longer than the minimum
input pulse width shown below.
Pulse width:....... 2 machine cycles (≥ 0.125µs for a 16MHz machine clock)
However, input pulses shorter than the above specification may be recognized as valid pulses in some
cases.
The PWC inputs do not have a filter function in the MB90580 series. If required, use a filter or similar
circuit externally.
262 Chapter 18: Pulse Width Counter (PWC) Timer
Table 18.4f Count Modes (Continued)
MOD2 MOD1 MOD0
0 1 0
0 1 1
Count Operation
(w: Pulse width being measured)
W
W
⇑ ⇓
Count start Count stop
⇓
Start
Measures the width between consecutive input edges.
• Count (measurement) start: Edge detected
• Count (measurement) end: Edge detected
W
⇓ ⇑
Count start Count stop
⇑
Start
(Divide by 4 example shown)
The input pulses are divided by the divide ratio set in
the divide ratio register (DIVR) and the resulting period
measured.
• Count (measurement) start: Falling edge detected
after operation started
• Count (measurement) end: End of one period of the
divided signal
W
⇑
Stop
⇑ ⇓
Start Stop
W W
⇓
Stop
and the timer counts up on
H
MB90580 Series