ST72F321J ST Microelectronics, ST72F321J Datasheet - Page 71

• Manufacturer Part Number: ST72F321J
• Description: 8-BIT MCU
• Manufacturer: ST Microelectronics

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DataSheet
16-BIT TIMER (Cont’d)
10.4.3.3 Input Capture
In this section, the index, i , may be 1 or 2 because
there are 2 input capture functions in the 16-bit
timer.
The two 16-bit input capture registers (IC1R and
IC2R) are used to latch the value of the free run-
ning counter after a transition is detected on the
ICAP i pin (see figure 5).
IC i R register is a read-only register.
The active transition is software programmable
through the IEDG i bit of Control Registers (CR i ).
Timing resolution is one count of the free running
counter: (
Procedure:
To use the input capture function select the follow-
ing in the CR2 register:
– Select the timer clock (CC[1:0]) (see
– Select the edge of the active transition on the
And select the following in the CR1 register:
– Set the ICIE bit to generate an interrupt after an
– Select the edge of the active transition on the
Clock Control
ICAP2 pin with the IEDG2 bit (the ICAP2 pin
must be configured as floating input or input with
pull-up without interrupt if this configuration is
available).
input capture coming from either the ICAP1 pin
or the ICAP2 pin
ICAP1 pin with the IEDG1 bit (the ICAP1pin must
be configured as floating input or input with pull-
up without interrupt if this configuration is availa-
ble).
4
ICiR
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CC[1:0]).
Bits).
MS Byte
IC i HR
LS Byte
IC i LR
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Table 17
When an input capture occurs:
– ICF i bit is set.
– The IC i R register contains the value of the free
– A timer interrupt is generated if the ICIE bit is set
Clearing the Input Capture interrupt request (i.e.
clearing the ICF i bit) is done in two steps:
1. Reading the SR register while the ICF i bit is set.
2. An access (read or write) to the IC i LR register.
Notes:
1. After reading the IC i HR register, transfer of
2. The IC i R register contains the free running
3. The 2 input capture functions can be used
4. In One pulse Mode and PWM mode only Input
5. The alternate inputs (ICAP1 & ICAP2) are
6. The TOF bit can be used with interrupt genera-
running counter on the active transition on the
ICAP i pin (see
and the I bit is cleared in the CC register. Other-
wise, the interrupt remains pending until both
conditions become true.
input capture data is inhibited and ICF i will
never be set until the IC i LR register is also
read.
counter value which corresponds to the most
recent input capture.
together even if the timer also uses the 2 output
compare functions.
Capture 2 can be used.
always directly connected to the timer. So any
transitions on these pins activates the input
capture function.
Moreover if one of the ICAP i pins is configured
as an input and the second one as an output,
an interrupt can be generated if the user tog-
gles the output pin and if the ICIE bit is set.
This can be avoided if the input capture func-
tion i is disabled by reading the IC i HR (see note
1).
tion in order to measure events that go beyond
the timer range (FFFFh).
Figure
45).
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