MULTIJUNCTION TIMERS
10.4 TIO (Input/Output-Related 16-Bit Timer)
10
10.4.9 Operation in TIO Measure Free-Run/ Clear Input Modes
(1) Outline of TIO measure free-run/ clear input modes
In measure free-run/ clear input modes, the timer is used to measure a duration of time from when the
counter starts counting till when an external capture signal is entered. An interrupt request can be generated
by a counter underflow or execution of a measure operation.
After the timer is enabled (by writing to the enable bit in software), the counter starts counting down synchro-
nously with the count clock. When a capture signal is entered from an external device, the counter value at
that point in time is written into a register called the “measure register.”
In measure clear input mode, the counter value is initialized to H’FFFF upon capture, from which the counter
starts counting down again. When the counter underflows, it starts counting down from H'FFFF.
In measure free-run input mode, the counter continues counting down even after capture and upon under-
flow, recycles to H’FFFF, from which it starts counting down again.
To stop the counter, disable count by writing to the enable bit in software.
Enabled
Measure event
(capture) occurs
(by writing to
the enable bit)
Measure event
(capture)
Count clock
Enable bit
H'FFFF
Undefined
value
H'9000
Counter
H'7000
H'0000
Undefined
H'7000
H'9000
Measure register
TIN interrupt request
TIN interrupt request due to
external event input
TIN interrupt request due to
external event input
TIO interrupt request
TIO interrupt request due
to underflow
Note: • This diagram does not show detailed timing information.
Figure 10.4.6 Typical Operation in Measure Free-Run Input Mode
32180 Group User’s Manual (Rev.1.0)
10-114
RENESAS [ RENESAS TECHNOLOGY CORP ]
