ST7FMC1K2B3 STMICROELECTRONICS [STMicroelectronics], ST7FMC1K2B3 Datasheet - Page 85

• Manufacturer Part Number: ST7FMC1K2B3
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

16-BIT TIMER (Cont’d)
10.3.3.5 One Pulse Mode
One Pulse mode enables the generation of a
pulse when an external event occurs. This mode is
selected via the OPM bit in the CR2 register.
The one pulse mode uses the Input Capture1
function and the Output Compare1 function.
Procedure:
To use one pulse mode:
1. Load the OC1R register with the value corre-
2. Select the following in the CR1 register:
3. Select the following in the CR2 register:
When a valid event occurs on the ICAP1 pin, the
counter value is loaded in the ICR1 register. The
counter is then initialized to FFFCh, the OLVL2 bit
is output on the OCMP1 pin and the ICF1 bit is set.
Because the ICF1 bit is set when an active edge
occurs, an interrupt can be generated if the ICIE
bit is set.
sponding to the length of the pulse (see the for-
mula in the opposite column).
– Using the OLVL1 bit, select the level to be ap-
– Using the OLVL2 bit, select the level to be ap-
– Select the edge of the active transition on the
– Set the OC1E bit, the OCMP1 pin is then ded-
– Set the OPM bit.
– Select the timer clock CC[1:0] (see
plied to the OCMP1 pin after the pulse.
plied to the OCMP1 pin during the pulse.
ICAP1 pin with the IEDG1 bit (the ICAP1 pin
must be configured as floating input).
icated to the Output Compare 1 function.
Clock Control
event occurs
on ICAP1
Counter
= OC1R
When
When
Bits).
One pulse mode cycle
OCMP1 = OLVL2
OCMP1 = OLVL1
Counter is reset
ICR1 = Counter
ICF1 bit is set
to FFFCh
Table 16
Clearing the Input Capture interrupt request (i.e.
clearing the ICFi bit) is done in two steps:
1. Reading the SR register while the ICFi bit is set.
2. An access (read or write) to the ICiLR register.
The OC1R register value required for a specific
timing application can be calculated using the fol-
lowing formula:
Where:
t
f
PRESC
If the timer clock is an external clock the formula is:
Where:
t
f
When the value of the counter is equal to the value
of the contents of the OC1R register, the OLVL1
bit is output on the OCMP1 pin, (See
Notes:
1. The OCF1 bit cannot be set by hardware in one
2. When the Pulse Width Modulation (PWM) and
3. If OLVL1=OLVL2 a continuous signal will be
4. The ICAP1 pin can not be used to perform input
5. When one pulse mode is used OC1R is dedi-
CPU
EXT
pulse mode but the OCF2 bit can generate an
Output Compare interrupt.
One Pulse Mode (OPM) bits are both set, the
PWM mode is the only active one.
seen on the OCMP1 pin.
capture. The ICAP2 pin can be used to perform
input capture (ICF2 can be set and IC2R can be
loaded) but the user must take care that the
counter is reset each time a valid edge occurs
on the ICAP1 pin and ICF1 can also generates
interrupt if ICIE is set.
cated to this mode. Nevertheless OC2R and
OCF2 can be used to indicate a period of time
has been elapsed but cannot generate an out-
put waveform because the level OLVL2 is dedi-
cated to the one pulse mode.
= Pulse period (in seconds)
= CPU clock frequency (in hertz)
= Timer prescaler factor (2, 4 or 8 depend-
= Pulse period (in seconds)
= External timer clock frequency (in hertz)
OCiR Value =
ing on the CC[1:0] bits, see
Clock Control
OCiR =
t
*
ST7MC1xx/ST7MC2xx
Bits)
f
EXT
PRESC
t
*
f
CPU
-5
- 5
Figure
Table 16
85/309
53).
1