ST10R272L - GENERAL PURPOSE TIMER UNITS
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DP3.3 to ‘1’. If T3OE=‘1’, pin T3OUT outputs the state of T3OTL. If T3OE=‘0’, pin T3OUT
can be used as general purpose IO pin.
T3OTL can also be used in conjunction with the timer over/underflows as an input for the
counter function or as a trigger source for the reload function of the auxiliary timers T2 and
T4. For this purpose, the state of T3OTL does not have to be available at pin T3OUT,
because an internal connection is provided for this option.
Timer 3 in timer mode
Timer mode for the core timer T3 is selected by setting bit field T3M in the T3CON register to
‘000
B
’. In this mode, T3 is clocked with the internal system clock (CPU clock) divided by a
programmable pre-scaler selected by bit field T3I. The input frequency
f
T3
for timer T3 and
its resolution
r
T3
are scaled linearly with lower clock frequencies
f
CPU
, as can be seen from
the following formula:
The timer resolutions which result from the selected pre-scaler option are listed in the table
below. This table also applies to the Gated Timer Mode of T3 and to the auxiliary timers T2
and T4 in timer and gated timer mode.
Figure 70 Block diagram of core timer T3 in timer mode
Timer Input Selection T2I / T3I / T4I
000
B
001
B
010
B
011
B
100
B
101
B
110
B
111
B
Table 32 GPT1 timer resolutions
f
T3
f
CPU
8
2
T3I
〈
〉
×
⁄
=
r
T3
µ
S
[
]
8
2
T3I
〈
〉
×
f
CPU
⁄
MHz
[
]
=
T3EUD = P3.4
T3OUT = P3.3
x = 3
