Fujitsu F2MC-16LX Hardware Manual page 314

CHAPTER 14 PWC TIMER
Table 14.3-6 List of measurement modes (Continued)
Measurement
MOD2
mode
Divide interval
0
measurement
In any mode, counting is not performed during the time from the start of counting to the input of
the count start edge. When the count start edge is input, the timer is cleared to 0000
timer counts until a count end edge is input. When a count end edge is entered, the following
operations are executed:
1. Set the PWCSR's measurement end flag (EDIR)
2. Stop the timer count operation (except in cases when the edge is input for a restart)
3. In repeated measurement mode, the timer value (measurement result) is transferred to the
PWCR, and the count operation is suspended until the next measurement start edge is
entered.
4. In one-shot measurement mode, the measurement will end (unless restart is entered at the
same time)
If, in repeated measurement mode, pulse width measurement between all edges or divide
measurement is performed, the end edge defines the next edge for measurement.
I Minimum input pulse width
The following restriction applies to pulses that are input to the pulse width measurement input
pins (PWC2 to PWC0):
The pulse width must be four machine cycles or more (0.25 µs for a 16 MHz machine clock).
•
I Pulse width/interval calculation method
The pulse width/interval to be measured can be calculated with the following formula:
T = n x t / D
W
Where
T : pulse width/interval to be measured [µs]
W
n: measurement result data in PWCR
t: count clock interval [µs]
298
MOD1 MOD0 Measurement items (W: pulse width to be measured)
1 1
(Example of divide-by-4)
Measures an interval by dividing the input pulse with a divide ratio
selected in the divide ratio set register DIVR
Start of counting (measurement): When a rising edge is detected
soon after the start
End of counting (measurement): When an interval ends after
dividing
[µ µ µ µ s]
IV
W
Start of counting
W W
Stop of counting
Stop
Start
H
, and the