Renesas 7700 FAMILY User Manual page 154

(2) Timer Bi overflow flag
The timer Bi interrupt request occurs when the measurement pulse's valid edge is input or the
counter overflows. The timer Bi overflow flag is used to identify the cause of the interrupt request,
that is, whether it is an overflow occurrence or an effective edge input.
The timer Bi overflow flag is set to "1" by an overflow. Accordingly, the cause of the interrupt request
occurrence is identified by checking the timer Bi overflow flag in the interrupt routine. When a value
is written to the timer Bi mode register with the count start bit = "1," the timer Bi overflow flag is
cleared to "0" at the next count timing of the count source
The timer Bi overflow flag is a read-only bit.
Use the timer Bi interrupt request bit to detect the overflow timing. Do not use the timer Bi overflow
flag to do that.
Figure 6.5.3 shows the operation during pulse period measurement. Figure 6.5.4 shows the operation
during pulse width measurement.
Count source
Measurement pulse
Reload register
transfer timing
Timing at which counter is
cleared to "0000
Count start bit
Timer Bi interrupt
request bit
Timer Bi overflow flag
Counter is initialized by completion of measurement.
Counter overflow.
Note: The above applies when measurement is performed for an interval from one falling to the next falling
of the measurement pulse.
Fig. 6.5.3 Operation during pulse period measurement
6.5 Pulse period/pulse width measurement mode
"H"
"L"
counter
"
16
"1"
"0"
"1"
"0"
"1"
"0"
7751 Group User's Manual
Transferred
(undefined value)
Cleared to "0" when interrupt request is accepted or
cleared by software.
TIMER B
Transferred
(measured value)
6–25