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16-BIT TIMER (Cont’d)

4.3.3.5 Forced Compare Mode

In this section

i may represent 1 or 2.

The following bits of the CR1 register are used:

When the FOLV

i bit is set, the OLVLi bit is copied

to the OCMP

i pin. The FOLVi bit is not cleared by

software, only by a chip reset. The OLV

i bit has to

be toggled in order to toggle the OCMP

i pin when

it is enabled (OC

iE bit=1).

The OCF

i bit is not set, and thus no interrupt

request is generated.

4.3.3.6 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, select the following in the

the CR1 register:

– Using the OLVL1 bit, select the level to be ap-

plied to the OCMP1 pin after the pulse.

– Using the OLVL2 bit, select the level to be ap-

plied to the OCMP1 pin during the pulse.

– Select the edge of the active transition on the

ICAP1 pin with the IEDG1 bit

And select the following in the CR2 register:

– Set the OC1E bit, the OCMP1 pin is then dedi-

cated to the Output Compare 1 function.

– Set the OPM bit.

– Select the timer clock CC1-CC0 (see Table 15

Clock Control Bits).

Load

the

OC1R

with

the

value

corresponding to the length of the pulse (see the

formula in Section 4.3.3.7).

Then, on a valid event on the ICAP1 pin, the

counter is initialized to FFFCh and OLVL2 bit is

loaded on the OCMP1 pin. 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 Figure 35).

Note: The OCF1 bit cannot be set by hardware in one

pulse mode but the OCF2 bit can generate an Out-

put Compare interrupt.

The ICF1 bit is set when an active edge occurs and

can generate an interrupt if the ICIE bit is set.

When the Pulse Width Modulation (PWM) and

One Pulse Mode (OPM) bits are both set, the

PWM mode is the only active one.

Figure 35.

One Pulse Mode Timing

FOLV2 FOLV1 OLVL2

OLVL1

event occurs

Counter is

initialized

to FFFCh

OCMP1 = OLVL2

Counter

= OC1R

OCMP1 = OLVL1

When

on ICAP1

One pulse mode cycle

COUNTER

....

FFFC FFFD FFFE

2ED0

2ED1 2ED2

2ED3

FFFC FFFD

OLVL2

OLVL1

ICAP1

OCMP1

compare1

Note: IEDG1=1, OC1R=2ED0h, OLVL1=0, OLVL2=1

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