dm00042534

AN4013
Application note
STM32 cross-series timer overview
Introduction
The purpose of this document is detailed hereafter:
• Present an overview of the timer peripherals in the STM32 product series detailed in
Table 1.
• Describe the various modes and specific features of the timers, such as clock sources.
• Explain how to use the available modes and features.
• Explain how to compute the time base in each configuration.
• Describe the timer synchronization sequences and the advanced features for motor
control applications, in addition to the general-purpose timer modes.
For each mode, typical configurations are presented and examples of how to use the modes
are provided.
In the rest of this document (unless otherwise specified), the term STM32xx is used to refer
to the products listed in Table 1.
Table 1. Applicable products
Type
Microcontrollers
April 2016
Product series
STM32F0 Series, STM32F1 Series, STM32F2 Series, STM32F3 Series,
STM32F4 Series, STM32F7 Series, STM32L0 Series, STM32L1 Series,
STM32L4 Series
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www.st.com
1
Contents
AN4013
Contents
1
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2
General-purpose timer modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.1
3
4
5
2/39
Clock input sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.1.1
Internal clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.1.2
External clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.2
Time base generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.3
Timer input capture mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.4
Timer output compare mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.5
Timer PWM mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.6
Timer one pulse mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.7
Timer Asymmetric PWM mode available for
STM32L4/F7 Series and STM32F30x/F3x8 lines . . . . . . . . . . . . . . . . . . 15
2.8
Timer combined PWM mode available for
STM32L4/F7 Series and STM32F30x/F3x8 lines . . . . . . . . . . . . . . . . . . 17
2.9
Retriggerable one pulse mode available for
STM32L4/F7 Series and STM32F30x/F3x8 lines . . . . . . . . . . . . . . . . . . 18
Timer synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
3.1
Timer system link . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
3.2
Master configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
3.3
Slave configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Advanced features for motor control . . . . . . . . . . . . . . . . . . . . . . . . . . 23
4.1
Signal generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
4.2
Combined three-phase PWM mode available for
STM32L4/F7 Series and STM32F30x/F3x8 lines . . . . . . . . . . . . . . . . . . 25
4.3
Specific features for motor control applications . . . . . . . . . . . . . . . . . . . . 26
4.3.1
Complementary signal and dead time feature . . . . . . . . . . . . . . . . . . . . 26
4.3.2
Break input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
4.3.3
Locking mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
4.3.4
Specific features for feedback measurement . . . . . . . . . . . . . . . . . . . . . 29
High-resolution timer applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
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7
8
Contents
Low-power timer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
6.1
Used as a wakeup timer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
6.2
Pulse counter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Specific applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
7.1
Infrared application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
7.2
3-phase AC and PMSM control motor . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
7.3
Six-step mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
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3
List of tables
AN4013
List of tables
Table 1.
Table 2.
Table 3.
Table 4.
Table 5.
Table 6.
Table 7.
4/39
Applicable products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Simplified overview of timer availability in STM32 products . . . . . . . . . . . . . . . . . . . . . . . . . 7
Timer features overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Advanced timer configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Behavior of timer outputs versus Break1 and Break2 inputs . . . . . . . . . . . . . . . . . . . . . . . 28
Locking levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
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List of figures
List of figures
Figure 1.
Figure 2.
Figure 3.
Figure 4.
Figure 5.
Figure 6.
Figure 7.
Figure 8.
Figure 9.
Figure 10.
Asymmetric PWM mode versus center Aligned PWM mode . . . . . . . . . . . . . . . . . . . . . . . 16
Combined PWM mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Retriggerable OPM mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Timer system link . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Combined three-phase PWM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Two signals are generated with insertion of a dead time . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Position at X4 resolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Position at X2 resolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Output waveform of a typical Hall sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Commutation sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
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5
Overview
1
AN4013
Overview
The STM32 devices are built-in with various types of timers, with the following features for
each:
•
General-purpose timers are used in any application for output compare (timing and
delay generation), one-pulse mode, input capture (for external signal frequency
measurement), sensor interface (encoder, hall sensor)...
•
Advanced timers: these timers have the most features. In addition to general purpose
functions, they include several features related to motor control and digital power
conversion applications: three complementary signals with deadtime insertion,
emergency shut-down input.
•
One or two channel timers: used as general-purpose timers with a limited number of
channels.
•
One or two channel timers with complementary output: same as previous type, but
having a deadtime generator on one channel. This allows having complementary
signals with a time base independent from the advanced timers.
•
Basic timers have no input/outputs and are used either as timebase timers or for
triggering the DAC peripheral.
•
Low-power timers are simpler than general purpose timers and their advantage is the
ability to continue working in low-power modes and generate a wake-up event.
•
High-resolution timers are specialized timer peripherals designed to drive power
conversion in lighting and power source applications. It is however also usable in other
fields that require very fine timing resolution. AN4885 and AN4449 are practical
examples of high-resolution timer use.
Table 2 summarizes the STM32 family timers.
Table 3 presents a general overview of timer features.
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Timer type
STM32
F04x
/F070x6
/F03x
(excluding
/F030x8
and
/F030x)
STM32
F030xB
/F030x8
/F05x
/F09x
/F07x
(excluding
F070x6)
STM32
F101
/F102
/F103
lines
XL
density
(xF, xG)
STM32
F101
/F102
/F103
/F105
/F107
lines up
to high
density
(x4-xE)
Advanced
TIM1
TIM1
TIM1(1)
TIM8(1)
32bit
TIM2
TIM2
16bit
TIM3
Basic
STM32
F100
value
line
STM32
F2
/F4
(excluding
/F401,
/F411,
/F410)
STM32
F401
/F411
/F410
STM32
F30X
/F3x8
(excluding
/F378)
TIM1(1)
TIM8(1)
TIM1
TIM1
TIM8
TIM1
TIM1
TIM8(1)
TIM20(1)
-
TIM1
-
-
-
TIM2
TIM5
TIM2(1)
TIM5
TIM2
TIM2
TIM5
TIM3
TIM2
TIM3
TIM4
TIM5
TIM2
TIM3
TIM4(1)
TIM5(1)
TIM2
TIM3
TIM4
TIM5(1)
TIM3
TIM4
TIM3(1)
TIM4(1)
TIM3(1)
TIM4(1)
TIM19(1)
-
TIM6
TIM7(1)
TIM6
TIM7
TIM6(1)
TIM7(1)
TIM6
TIM7
TIM6
TIM7
TIM6(1)
1 channel
TIM14
TIM14
TIM10
TIM11
TIM13
TIM14
-
TIM13(1)
TIM14(1)
TIM10
TIM11
TIM13
TIM14
2-channel
-
-
TIM9
TIM12
-
TIM12(1)
2-channel with
complementary
output
-
TIM15
-
-
1-channel with
complementary
output
TIM16
TIM17
TIM16
TIM17
-
Low-power
timer
-
-
High-resolution
timer
-
-
General
purpose
AN4013
Table 2. Simplified overview of timer availability in STM32 products
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STM32
F7
Series
STM32
L05X
/L06x
/L07x
/L08x
lines
STM32
L03x
/L02x
/L01x
lines
STM32
L1
Series
STM32
L4
Series
TIM1
TIM8(1)
TIM1
TIM8
-
-
-
TIM1
TIM8(1)
TIM2
TIM2
TIM2
TIM5
-
-
TIM5(1)
TIM2
TIM5(1)
TIM3
TIM4
TIM19
TIM3
TIM3
TIM4
TIM3
TIM4
TIM2
TIM3(1)
TIM2
TIM2
TIM3
TIM4
TIM3(1)
TIM4(1)
TIM6
TIM7(1)
TIM6
TIM7
TIM18
TIM6
TIM7
TIM6
TIM7(1)
TIM6
TIM7
TIM6
TIM7(1)
-
TIM6
TIM7
TIM6
TIM7
TIM10(1)
TIM11
-
TIM13
TIM14
-
-
TIM10
TIM11
TIM13
TIM14
-
-
TIM10
TIM11
-
TIM9
TIM12
TIM9
-
TIM12
-
-
TIM9
TIM12
TIM21
TIM22
TIM21
TIM22(1)
TIM9
-
TIM15
-
-
TIM15
TIM15
TIM15
TIM15
-
-
-
-
TIM15
-
TIM16
TIM17
-
-
TIM16
TIM17
TIM16
TIM17
TIM16
TIM17
TIM16
TIM17
-
-
-
-
TIM16
TIM17(1)
-
-
-
-
LPTIM1(1)
-
-
-
-
LPTIM1
-
LPTIM1
LPTIM2
-
-
-
-
-
-
-
HRTIM
-
-
-
-
STM32 STM32 STM32
F37x
F334
F31x
LPTIM1 LPTIM1
-
-
1. Not available on all products in the line. Please check the datasheet for details.
More recent versions of advanced timers present several new modes: asymmetric mode, combined mode, one retriggerable
mode, combined 3 PWM mode and a second break input, these modes are available only for STM32L4/F7 Series and
STM32F30x/F3x8 lines.
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Overview
Note:
Overview
AN4013
Table 3. Timer features overview
Synchronization
Counter
resolution
Counter type
DMA
Channels
Comp.
channels
16 bit
Up, down and
center aligned
Yes
4, 6(1)
16 bit
32 bit(2)
Up, down and
center aligned
Yes
Basic
16 bit
Up
1-channel
16 bit
2-channel
Timer type
Master
config.
Slave
config.
3
Yes
Yes
4
0
Yes
Yes
Yes
0
0
Yes
No
Up
No
1
0
Yes (OC
signal)
No
16 bit
Up
No
2
0
Yes
Yes
1-channel with one
complementary
output
16 bit
Up
Yes
1
1
Yes (OC
signal)
No
2-channel with one
complementary
output
16 bit
Up
Yes
2
1
Yes
Yes
Low-power timer
16 bit
Up
No
1(3)
0
Yes (OC
signal)
No
High-resolution
timer
16 bit
Up
Yes
5(3)
5
Yes
Yes
Advanced
General-purpose
1. With STM32L4/F7 series and STM32F30x/F3x8 lines the advanced timers have 6 channels. The two extra channels are
however not connected to GPIO (not available as output).
2. TIM2 and TIM5 are 32-bit counter resolution some products and 16-bit in others. See Table 2 or product datasheet as
reference.
3. Low-power timer and high-resolution timer do not have channels directly comparable with channels on regular timer
peripherals. Indicated number is a “channel equivalent”.
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AN4013
General-purpose timer modes
2
General-purpose timer modes
General-purpose timers can be programmed to work in various different configurations.
Following chapter is an introduction to the timer usage.
2.1
Clock input sources
The timer always needs a clock source. It also can be synchronized by several clocks
simultaneously:
2.1.1
•
Internal clock
•
External clock
–
External mode1 (TI1 or TI2 pins)
–
External clock mode2 (ETR pin)
–
Internal trigger clock (ITRx).
Internal clock
The timer is clocked by default by the internal clock provided from the RCC. To select this
clock source, the TIMx_SMCR->SMS (if present) bits should be reset.
2.1.2
External clock
The external clock timer is divided in two categories:
•
External clock connected to TI1 or TI2 pins
•
External clock connected to ETR pin
In these cases, the clock is provided by an external signal connected to TIx pins or ETR pin.
The maximum external clock frequency should be verified.
Note:
1
In addition to all these clock sources, the timer should be clocked with the APBx clock.
2
The external clocks are not directly feeding the prescaler, but they are first synchronized
with the APBx clock through dedicated logical blocks.
External clock mode1 (TI1 or TI2 pins)
In this mode the external clock will be applied on timer input TI1 pin or TI2 pin. To do this:
1.
Configure the timers to use the TIx pin as input:
a)
Select the pin to be used by writing CCxS bits in the TIMx_CCMR1 register.
b)
Select the polarity of the input:
For the STM32F100/101/102/103/105/107 lines: by writing CCxP in the
TIMx_CCER register to select the rising or the falling edge;
For the other series & lines: by writing CCxP and CCxNP in the TIMx_CCER
register to select the rising/falling edge, or both edges(a).
c)
Enable corresponding channel by setting the CCEx bit in the TIMx_CCER register.
2.
Select the timer TIx as the trigger input source by writing TS bits in the TIMx_SMCR
register.
3.
Select the external clock mode1 by writing SMS=111 in the TIMx_SMCR register.
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General-purpose timer modes
AN4013
External clock mode2 (ETR pin)
The external clock mode2 uses the ETR pin as timer input clock. To use this feature:
1.
Select the external clock mode2 by writing ECE = 1 in the TIMx_SMCR register.
2.
Configure, if needed, the prescaler, the filter and the polarity by writing ETPS [1:0], ETF
[3:0] and ETP in the TIMx_SMCR register.
Internal trigger clock (ITRx)
This is a particular mode of timer synchronization. When using one timer as a prescaler for
another timer, the first timer update event or output compare signal is used as a clock for the
second one.
2.2
Time base generator
The timer can be used as a time base generator. Depending on the clock, prescaler and
auto reload, repetition counter (if present) parameters, the 16-bit timer can generate an
update event from a nanosecond to a few minutes. For the 32-bit timer, the range is larger.
Example update event period
The update event period is calculated as follows:
Update_event = TIM_CLK/((PSC + 1)*(ARR + 1)*(RCR + 1))
Where: TIM_CLK = timer clock input
PSC = 16-bit prescaler register
ARR = 16/32-bit Autoreload register
RCR = 16-bit repetition counter
TIM_CLK = 72 MHz
Prescaler = 1
Auto reload = 65535
No repetition counter RCR = 0
Update_event = 72*106/((1 + 1)*(65535 + 1)*(1))
Update_event = 549.3 Hz
a. For the STM32F100/101/102/103/105/107 lines, polarity selection for both edges can be achieved by using
TI1F_ED, but only for TI1 input.
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General-purpose timer modes
Example external clock mode2
In this mode, the update event period is calculated as follows:
Update_event = ETR_CLK/((ETR_PSC)*(PSC + 1)*(ARR + 1)*(RCR + 1))
Where ETR_CLK = the external clock frequency connected to ETR pin.
ETR_CLK = 100 kHz
Prescaler = 1
ETPS - external trigger prescaler= 2
Autoreload = 255
Repetition counter = 2
Update_event= 100*103/((2)* (1+ 1)*((255 + 1)*(2 + 1))
Update_event = 21.7 Hz
Example external clock mode1
In this mode, the update event period is calculated as follows:
Update_event = TIx_CLK/((PSC + 1)*(ARR + 1)*(RCR +1))
Where TIx_CLK = the external clock frequency connected to TI1 pin or TI2 pin.
TIx_CLK = 50 kHz
Prescaler = 1
Auto reload = 255
Repetition counter = 2
Update_event = 50 000/((1+ 1)*((255 + 1)*(2 + 1))
Update_event = 32.55 Hz
Example Internal trigger clock (ITRx) mode1
In this mode, the update event period is calculated as follows:
Update_event = ITRx_CLK/((PSC + 1)*(ARR + 1)*(RCR + 1))
Where ITRx_CLK = the internal trigger frequency mapped to timer trigger input (TRGI)
ITRx_CLK = 8 kHz
Prescaler = 1
Auto reload = 255
Repetition counter = 1
Update_event = 8000/((1+ 1)*((255 + 1)*(1 + 1))
Update_event = 7.8 Hz
Depending on the counter mode, the update event is generated each:
•
Overflow, if up counting mode is used: the DIR bit is reset in TIMx_CR1 register
•
Underflow, if down counting mode is used: the DIR bit is set in TIMx_CR1 register
•
Overflow and underflow, if center aligned mode is used: the CMS bits are different from
zero.
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38
General-purpose timer modes
AN4013
The update event is generated also by:
•
Software, if the UG (update generation) bit is set in TIM_EGR register.
•
Update generation through the slave mode controller
As the buffered registers (ARR, PSC, CCRx) need an update event to be loaded with their
preload values, set the URS (Update Request Source) to 1 to avoid the update flag each
time these values are loaded. In this case, the update event is only generated if the counter
overflow/underflow occurs.
The update event can be also disabled by setting the bit UDIS (update disable) in the CR1
register. In this case, the update event is not generated, and shadow registers (ARR, PSC,
CCRx) keep their value. The counter and the prescaler are reinitialized if the UG bit is set, or
if a hardware reset is received from the slave mode controller.
An interrupt or/ and a DMA request can be generated when the UIE bit or/and UDE bit are
set in the DIER register.
Most STM32Cube firmware packages include examples in Examples\TIM\TIM_TimeBase
subfolders.
2.3
Timer input capture mode
The timer can be used in input capture mode to measure an external signal. Depending on
timer clock, prescaler and timer resolution, the maximum measured period is deduced.
To use the timer in this mode:
1.
Select the active input by setting the CCxS bits in CCMRx register. These bits should
be different from zero, otherwise the CCRx register will be read only.
2.
Program the filter by writing the IC1F[3:0] bits in the CCMRx register, and the prescaler
by writing the IC1PSC[1:0] if needed.
3.
Program the polarity by writing the CCxNP/CCxP bits to select between rising, falling or
both edges.
The input capture module is used to capture the value of the counter after a transition is
detected by the corresponding input channel. To get the external signal period, two
consecutive captures are needed. The period is calculated by subtracting these two values.
Period = Capture(1) /(TIMx_CLK *(PSC+1)*(ICxPSC)*polarity_index(2))
The capture difference between two consecutive captures CCRx_tn and CCRx_tn+1:
•
If CCRx_tn < CCRx_tn+1: capture = CCRx_tn+1 - CCRx_tn
•
If CCRx_tn > CCRx_tn+1: capture = (ARR_max - CCRx_tn) + CCRx_tn+1
The polarity index is 1 if the rising or falling edge is used, and 2 if both edges are used.
Particular case
To facilitate the input capture measurement, the timer counter is reset after each rising edge
detected on the timer input channel by:
12/39
•
selecting TIxFPx as the input trigger by setting the TS bits in the SMCR register
•
selecting the reset mode as the slave mode by configuring the SMS bits in the SMCR
register
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AN4013
General-purpose timer modes
Using this configuration, when an edge is detected, the counter is reset and the period of the
external signal is automatically given by the value on the CCRx register. This method is
used only with channel 1 or channel 2.
In this case, the input capture prescaler (ICPSC) is not considered in the period
computation.
The period is computed as follows:
Period = CCRx /(TIMx_CLK *(PSC+1)* polarity_index(1))
The polarity index is 1 if rising or falling edge is used, and 2 if both edges are used.
Many STM32Cube firmwares package include examples in
Examples\TIM\TIM_InputCapture subfolder.
2.4
Timer output compare mode
To control an output waveform, or to indicate when a period of time has elapsed, the timer is
used in one of the following output compare modes. The main difference between these
modes is the output signal waveform.
•
Output compare timing: The comparison between the output compare register CCRx
and the counter CNT has no effect on the outputs. This mode is used to generate a
timing base.
•
Output compare active: Set the channel output to active level on match. The OCxRef
signal is forced high when the counter (CNT) matches the capture/compare register
(CCRx).
•
Output compare inactive: Set channel to inactive level on match. The OCxRef signal
is forced low when the counter (CNT) matches the capture/compare register (CCRx).
•
Output compare toggle: OCxRef toggles when the counter (CNT) matches the
capture/compare register (CCRx).
•
Output compare forced active/inactive: OCREF is forced high (active mode) or low
(inactive mode) independently from counter value.
To configure the timer in one of these modes:
1.
Select the clock source.
2.
Write the desired data in the ARR and CCRx registers.
3.
Configure the output mode:
a)
Select the output compare mode: timing / active / inactive / toggle.
b)
In case of active, inactive and toggle modes, select the polarity by writing CCxP in
CCER register.
c)
Disable the preload feature for CCx by writing OCxPE in CCMRx register.
d)
Enable the capture / compare output by writing CCxE in CCMRx register.
4.
Enable the counter by setting the CEN bit in the TIMx_CR1 register.
5.
Set the CCxIE / CCxDE bit if an interrupt / DMA request is to be generated.
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38
General-purpose timer modes
AN4013
Timer output compare timing / delay computation
CCx update rate = CK_CNT / TIMx_CCRx
CCx delay = CCRx / CK_CNT
•
If internal clock: CK_CNT= CK_PSC / (PSC + 1)
•
If external clock mode2: CK_CNT = CK_PSC / ((ETPS)*(PSC + 1))
•
If external clock mode1: CK_CNT = CK_PSC / (PSC + 1)
–
if ETRF used as clock source: CK_PSC = ETR_CLK / ETPS
–
if TIxFPx used as clock source: CK_PSC = TIx_CLK / ICPS
–
if TI1F_ED (filtered edge detection) used as clock source: CK_PSC =
TI1_ED_CLK
–
if ITRx (another timer) used as clock source: CK_PSC = ITRx_CLK
For more details on using the timer in this mode, refer to the examples provided in the
STM32Cube package libraries in Examples\TIM\TIM_OCToggle, \TIMxOCActive and
\TIM_OCInactive subfolders.
2.5
Timer PWM mode
The timer is able to generate PWM in edge-aligned mode or in center-aligned mode with a
frequency determined by the value of the TIMx_ARR register, and a duty cycle determined
by the value of the TIMx_CCRx register.
PWM mode 1
•
In up-counting, channelx is active as long as CNT< CCRx, otherwise it is inactive.
•
In down-counting, channelx is inactive as long as CNT> CCRx, otherwise it is active.
PWM mode 2
Note:
•
In up-counting, channelx is inactive as long as CNT < CCRx, otherwise it is active.
•
In down-counting, channelx is active as long as CNT > CCRx, otherwise it is inactive.
Active when OCREF = 1, inactive when OCREF = 0.
To configure the timer in this mode:
1.
2.
14/39
Configure the output pin:
a)
Select the output mode by writing CCS bits in CCMRx register.
b)
Select the polarity by writing the CCxP bit in CCER register.
Select the PWM mode (PWM1 or PWM2) by writing OCxM bits in CCMRx register.
3.
Program the period and the duty cycle respectively in ARR and CCRx registers.
4.
Set the preload bit in CCMRx register and the ARPE bit in the CR1 register.
5.
Select the counting mode:
a)
PWM edge-aligned mode: the counter must be configured up-counting or downcounting.
b)
PWM center aligned mode: the counter mode must be center aligned counting
mode (CMS bits different from '00').
6.
Enable the capture compare.
7.
Enable the counter.
DocID022500 Rev 5
AN4013
General-purpose timer modes
For more details on using the timer in this mode, refer to the STM32Cube F3 firmware
package examples in the Examples\TIM\TIM_PWMOutput subfolders.
2.6
Timer one pulse mode
One pulse mode (OPM) is a particular case of the input capture mode and the output
compare mode. It allows the counter to be started in response to a stimulus and to generate
a pulse with a programmable length after a programmable delay.
To configure the timer this mode:
1.
2.
3.
Configure the input pin and mode:
a)
Select the TIxFPx trigger to be used by writing CCxS bits in CCMRx register.
b)
Select the polarity of the input pin by writing CCxP and CCxNP bits in CCER
register.
c)
Configure the TIxFPx trigger for the slave mode trigger by writing TS bits in SMCR
register.
d)
Select the trigger mode for the slave mode by writing SMS = 110 in SMCR
register.
Configure the output pin and mode:
a)
Select the output polarity by writing CCyP bit in CCER register.
b)
Select the output compare mode by writing OCyM bits in CCMRy register (PWM1
or PWM2 mode).
c)
Set the delay value by writing in CCRy register.
d)
Set the auto reload value to have the desired pulse: pulse = TIMy_ARR TIMy_CCRy.
Select the one pulse mode by setting the OPM bit in CR1 register, if only one pulse is to
be generated. Otherwise this bit should be reset.
Delay = CCRy/(TIMx_CLK/(PSC + 1))
Pulse-Length = (ARR - CCRy)/(TIMx_CLK/(PSC + 1))
For more details on using the timer in this mode refer to the examples provided in the
STM32Cube package in the Examples\TIM\TIM_OnePulse subfolder.
2.7
Timer Asymmetric PWM mode available for
STM32L4/F7 Series and STM32F30x/F3x8 lines
The asymmetric mode allows generating a center-aligned PWM signals with a
programmable phase shift.
For a dedicated channel, the phase shift and the pulse length are programmed using the
two TIMx_CCRx register (TIMx_CCR1 and TIMx_CCR2 or TIMx_CCR3 and TIMx_CCR4),
the frequency is determined by the value of the TIMx_ARR register. So the asymmetric
PWM mode can be selected independently on two channels by programming the OCxM bits
in TIMx_CCMRx register:
•
OCxM = 1110 to use the Asymmetric PWM1, in this mode the output reference has
the same behavior as in PWM1 mode. When the counter is counting up the output
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38
General-purpose timer modes
AN4013
reference is identical to OC1/3REF, when the counter is down counting, the output
reference is identical to OC2/4REF
•
OCxM = 1111 to use the Asymmetric PWM2, in this mode the output reference has the
same behavior as in PWM2 mode. When the counter is counting up the output
reference is identical to OC1/3REF, when the counter is down counting, the output
reference is identical to OC2/4REF
The following figure resumes the asymmetric behavior versus the center aligned PWM
mode:
Figure 1. Asymmetric PWM mode versus center Aligned PWM mode
3:0FHQWHUDOLJQHG$55 DQG
&&5[ 3:0FHQWHUDOLJQHG$55 DQG
&&5\ $V\PHWULF3:0FHQWHUDOLJQHG$55 &&5[ DQG&&5\ 069
To configure the timer in this mode:
1.
16/39
Configure the output pin:
a)
Select the output mode by writing CCS bits in CCMRx register.
b)
Select the polarity by writing the CCxP bit in CCER register.
2.
Select the Asymmetric PWM mode (Asymmetric PWM1 or Asymmetric PWM2) by
writing OCxM bits in CCMRx register.
3.
Program the period, the pulse length and the phase shift respectively in ARR, CCRx
and CCRy registers.
4.
Select the counting mode: the Asymmetric PWM mode is working only with center
aligned mode: the counter mode must be center aligned counting mode (CMS bits
different from '00').
5.
Enable the capture compare.
6.
Enable the counter.
DocID022500 Rev 5
AN4013
General-purpose timer modes
STM32Cube F3 firmware package includes examples in the following directories:
2.8
•
Projects\STM32F3-Discovery\Examples\TIM\TIM_Asymetric,
•
Projects\STM32303E_EVAL\Examples\TIM\TIM_Asymetric
•
Projects\STM32303C_EVAL\Examples\TIM\TIM_Asymetric.
Timer combined PWM mode available for
STM32L4/F7 Series and STM32F30x/F3x8 lines
The combined mode allows generating edge or center aligned PWM signals with
programmable delay and phase shift between respective pulses.
To generate a combined signal, the TIMx_CCRx and TIMx_CCRy must be used to program
the delay and the phase shift. The frequency is determined by the value of the TIMx_ARR
register.
The resulting signal (combined signal) is made of an OR or AND logical combination of two
reference PWMs. So the combined PWM mode can be selected independently on two
channels by programming the OCxM bits in TIMx_CCMRx register:
•
OCxM = 1100 to use the Combined PWM1, in this case the combined output reference
has the same behavior as in PWM mode 1. The combined output reference is the
logical OR between OC1/3REF and OC2/4REF
•
OCxM = 1101 to use the Combined PWM2,in this case the combined output reference
has the same behavior as in PWM mode 2. The combined output reference is the
logical AND between OC1/2REF and OC2/4REF
The following figures resume the combined mode:
Figure 2. Combined PWM mode
2&5HI3:0
2&5HI3:0
2&&5HI
&RPELQHG3:0
2&5HI3:0
2&5HI3:0
2&&5HI
&RPELQHG3:0
069
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38
General-purpose timer modes
AN4013
To configure the timer in this mode:
1.
2.9
Configure the output pin:
a)
Select the output mode by writing CCS bits in CCMRx register.
b)
Select the polarity by writing the CCxP bit in CCER register.
2.
Select the Combined PWM mode (Combined PWM1 or Combined PWM2) by writing
OCxM bits in CCMRx register.
3.
Program the period, the delay and the phase shift respectively in ARR, CCRx and
CCRy registers.
4.
Select the counting mode:
a)
Edge-aligned mode: the counter must be configured up-counting or downcounting.
b)
Center aligned mode: the counter mode must be center aligned counting mode
(CMS bits different from '00')
5.
Enable the capture compare.
6.
Enable the counter.
Retriggerable one pulse mode available for
STM32L4/F7 Series and STM32F30x/F3x8 lines
The Retriggerable one pulse mode is a one pulse mode with the particularity of:
•
The pulse starts as soon as the trigger occurs (no programmable delay)
•
The pulse is extended if a new trigger occurs before the previous one is completed
If the counter is configured in up-counting mode, the corresponding CCRx must be set to 0,
in this case the pulse length is determined by ARR register. If the timer is configured in
down-counting mode, the ARR must be set to 0 in this case the pulse length is determined
by CCRx register. As for the OPM mode, there are two Retriggerable one pulse mode,
Retriggerable OPM mode 1 and Retriggerable OPM mode 2:
•
•
18/39
Retriggerable OPM mode 1 is selected by setting the OCXM bits to 1000:
–
In up-counting mode, channel is inactive until a trigger event is detected (on TRGI
signal), the comparison is performed like in PWM mode 1, then the channel
becomes inactive again at the next update.
–
In down-counting mode, channel is active until a trigger event is detected (on
TRGI signal), the comparison is performed like in PWM mode 1, then the channel
becomes active again at the next update.
Retriggerable OPM mode 2 i s selected by setting the OCXM bits to 1001:
–
In up-counting mode, the channel is active until a trigger event is detected (on
TRGI signal), the comparison is performed like in PWM mode 2, then the channel
becomes inactive again at the next update.
–
In down-counting mode, the channel is inactive until a trigger event is detected (on
TRGI signal), the comparison is performed like in PWM mode 1, then the channel
becomes inactive again at the next update.
DocID022500 Rev 5
AN4013
General-purpose timer modes
The following figure presents an example of the Retriggerable OPM mode
Figure 3. Retriggerable OPM mode
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3XOVHOHQJWK
5HWULJJHUDEOHSXOVHOHQJWK
3XOVHOHQJWK
3XOVHOHQJWK
2&[
069
To configure the timer in this mode:
1.
2.
Configure the input pin and mode:
a)
Select the TIxFPx trigger to be used by writing CCxS bits in CCMRx register.
b)
Select the polarity of the input pin by writing CCxP and CCxNP bits in CCER
register.
c)
Configure the TIxFPx trigger for the slave mode trigger by writing TS bits in SMCR
register.
d)
Select the Combined Reset + trigger mode for the slave mode by writing SMS =
1000 in SMCR register.
Configure the output pin and mode:
a)
Select the output polarity by writing CCyP bit in CCER register.
b)
Select the output compare mode by writing OCyM bits in CCMRy register
(Retriggerable OPM mode 1 or Retriggerable OPM mode 2).
c)
Set the Pulse length value by writing in CCRy register if the counter is downcounting or by writing in the ARR if the counter is up-counting.
For more details on using the timer in this mode, refer to the examples provided in the
STM32F30x standard peripheral libraries, in the
/Project/STM32F30x_StdPeriph_Examples/ TIM/Retriggerable OPM folder.
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38
Timer synchronization
AN4013
3
Timer synchronization
3.1
Timer system link
STM32 timers are linked together internally for timer synchronization or chaining. Each timer
has several internal trigger inputs and outputs. These signals allow the timer to be
connected with other timers.
Figure 4. Timer system link
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7,0[B&/.
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75*,
7ULJJHU
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3.2
Master configuration
When a timer is selected as a master timer, the corresponding trigger output signal is used
by the slave internal trigger (when configured). The trigger output can be selected from the
following list:
20/39
•
Reset: the UG bit from the TIMx_EGR register is used as a trigger output (TRGO).
•
Enable: the counter enable signal is used as a trigger output (TRGO). It is used to start
several timers at the same time, or to control a window in which a slave timer is
enabled.
•
Update: the update event is selected as trigger output (TRGO). For example, a master
timer can be used as a prescaler for a slave timer.
•
Compare pulse: the trigger output sends a positive pulse when the CC1IF flag is to be
set (even if it was already high) as soon as a capture or a compare match occurs.
•
OC1Ref: OC1REF signal is used as trigger output (TRGO).
•
OC2Ref: OC2REF signal is used as trigger output (TRGO).
•
OC3Ref: OC3REF signal is used as trigger output (TRGO).
•
OC4Ref: OC4REF signal is used as trigger output (TRGO).
DocID022500 Rev 5
AN4013
Timer synchronization
To configure a timer in master mode:
1.
Configure the timer.
2.
Select the trigger output to be used, by writing the MSM (Master Mode Selection) bits in
TIMx_CR2 register.
3.
Enable the MSM (Master/slave mode) bit in the SMCR register to allow a perfect
synchronization between the current timer and its slaves (through TRGO).
For the STM32F30x and STM32F3x8 the advanced-control timer can generate two trigger
outputs: TRGO as described above and TRGO2 (used for TIM and ADC synchronization)
which can be selected from the following list:
•
Reset - the UG bit from the EGR register is used as trigger output (TRGO2).
•
Enable - the Counter Enable signal CNT_EN is used as trigger output (TRGO2). It is
useful to start several timers at the same time or to control a window in which a slave
timer is enable. The Counter Enable signal is generated by a logic OR between CEN
control bit and the trigger input when configured in gated mode.
•
Update - The update event is selected as trigger output (TRGO2). For instance a
master timer can then be used as a prescaler for a slave timer.
•
Compare Pulse - The trigger output send a positive pulse when the CC1IF flag is to be
set (even if it was already high), as soon as a capture or a compare match occurred.
•
Compare - OC1REF signal is used as trigger output (TRGO2).
•
Compare - OC2REF signal is used as trigger output (TRGO2).
•
Compare - OC3REF signal is used as trigger output (TRGO2).
•
Compare - OC4REF signal is used as trigger output (TRGO2).
•
Compare - OC5REF signal is used as trigger output (TRGO2).
•
Compare - OC6REF signal is used as trigger output (TRGO2).
•
Compare Pulse - OC4REF rising or falling edges generate pulses on TRGO2.
•
Compare Pulse - OC6REF rising or falling edges generate pulses on TRGO2.
•
Compare Pulse - OC4REF rising or OC6REF rising edges generate pulses on TRGO2.
•
Compare Pulse - OC4REF rising or OC6REF falling edges generate pulses on
TRGO2.
•
Compare Pulse - OC5REF rising or OC6REF rising edges generate pulses on TRGO2.
•
Compare Pulse - OC5REF rising or OC6REF falling edges generate pulses on
TRGO2.
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Timer synchronization
3.3
AN4013
Slave configuration
The slave timer is connected to the master timer through the input trigger. Each ITRx is
connected internally to another timer, and this connection is specific for each STM32
product.
The slave mode can be:
•
Reset mode: rising edge of the selected trigger input (TRGI) reinitializes the counter
and generates an update of the registers.
•
Gated mode: the counter clock is enabled when the trigger input (TRGI) is high. The
counter stops (but is not reset) as soon as the trigger becomes low. Both start and stop
of the counter are controlled.
•
Trigger mode: the counter starts at a rising edge of the trigger TRGI (but it is not
reset). Only the start of the counter is controlled.
•
External clock mode 1: rising edges of the selected trigger (TRGI) clock the counter.
•
Combined Reset + Trigger Mode - Rising edge of the selected trigger input (TRGI)
reinitializes the counter, generates an update of the registers and starts the counter.
This mode is present only for STM32L4/F7 Series and STM32F30x/F3x8 lines.
To configure a timer in slave mode:
1.
Select the slave mode to be used by writing SMS (Slave Mode Selection) bits in SMCR
register.
2.
Select the internal trigger to be used by writing TS (Trigger selection) bits in SMCR
register
For more details on using the timer in this mode, refer to the examples provided in the
STM32Cube package in the
Examples\TIM\TIM_CascadeSynchro,\TIM_ExtTriggerSynchro\TIM_Synchronization and
\TIM_ParallelSynchro folders.
22/39
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Advanced features for motor control
4
Advanced features for motor control
4.1
Signal generation
The STM32 timer can output two complementary signals and manage the switching-off and
the switching-on instants of the outputs.
The complementary signals OCx and OCxN are activated by a combination of several
control bits: the CCxE and CCxNE and the MOE, OISx, OISxN, OSSI and OSSR bits.
The main output enable (MOE) bit is reset as soon as a break input is active. It is set by
software or automatically, depending on the automatic output enable (AOE) bit. When this
bit (MOE) is reset, the OCx and OCxN outputs are disabled or forced to idle state (OISx
OISxN), depending on whether the OSSI bit is set or not.
Note:
The MOE bit is valid only on the channels that are configured in output.
The Off-state selection for Run mode (OSSR) bit is used when MOE=1 on channels that
have a complementary output configured as outputs. When this bit is set, OCx and OCxN
outputs are enabled with their inactive level as soon as CCxE=1 or CCxNE=1. The output is
still controlled by the timer.
The Off-state selection for Idle mode (OSSI) bit is used when MOE=0 due to a break event
or by a software write, on channels configured as outputs. When this bit is set, OCx and
OCxN outputs are first forced with their inactive level, then forced to their idle level after the
dead time. The timer maintains its control over the output.
Table 4 explains the possible configurations of the advanced timer.
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Advanced features for motor control
AN4013
Table 4. Advanced timer configurations
Control bits
MOE
1
MOE
0
Note:
24/39
Output state
Typical use
OSSI
OSSR
OCxE
OCxNE
OCx output
state
OCxN output
state
x
0
0
0
Output disable
Output disable
x
0
0
1
Output disable
OCxREF
+ Polarity
x
0
1
0
OCxREF
+ Polarity
Output disable
x
0
1
1
OCxREF
+ Polarity
+ Deadtime
(not OCxREF)
+ Polarity
+ Deadtime
x
1
0
0
Output disabled
Output disabled
x
1
0
1
Off-state
OCxREF
+ Polarity
x
1
1
0
OCxREF +
Polarity
Off-state
x
1
1
1
OCxREF
+ Polarity
+ Deadtime
(not OCxREF)
+ Polarity
+ Deadtime
Motor control
(sinewave)
OSSI
OSSR
OCxE
OCxNE
OCx output
state
OCxN output
state
Comments
0
x
0
0
0
x
0
1
0
x
1
0
0
x
1
1
1
x
0
0
1
x
0
1
1
x
1
0
1
x
1
1
Output disable
Off-state
(outputs are first forced with their
inactive level then forced to their
idle level after the deadtime.)
General purpose
Motor control
(sinewave)
Motor control
(6-steps)
Outputs
disconnected
from I/O ports
All PWMs OFF
(low Z for safe
stop)
1
Dead time insertion is enabled by setting both CCxE and CCxNE bits, and the MOE bit.
2
When only OCxN is enabled (CCxE=0, CCxNE=1), it is not complemented and becomes
active as soon as OCxREF is high. For example, if CCxNP=0 then OCxN=OCxRef. On the
other hand, when both OCx and OCxN are enabled (CCxE=CCxNE=1) OCx becomes
active when OCxREF is high, whereas OCxN is complemented and becomes active when
OCxREF is low.
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4.2
Advanced features for motor control
Combined three-phase PWM mode available for
STM32L4/F7 Series and STM32F30x/F3x8 lines
The combined three-phase mode allows generating one to three center-aligned PWM
signals with a single programmable signal ANDed in the middle of the pulses. this
configuration is helpful for shunt resistor current sensing applications. Refer to UM1052 for
further reading on this topic.
Using the 3-bits GC5C[3:1] in the TIMx_CCR5, each channel of the TIM can be a
combination between the original signal and the OC5Ref signal:
•
If GC5C1 is set, OC1 output is controlled by TIMx_CCR1 and TIMx_CCR5
•
If GC5C2 is set, OC1 output is controlled by TIMx_CCR2 and TIMx_CCR5
•
If GC5C3 is set, OC1 output is controlled by TIMx_CCR3 and TIMx_CCR5
The following figure presents an example of this mode:
Figure 5. Combined three-phase PWM
2&5HI
2&5HI
2&5HI
2&5HI
2&5HI&RPE
2&5HI&RPE
2&5HI&RPE
069
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Advanced features for motor control
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To configure the timer in this mode:
1.
2.
Configure the output pin:
a)
Select the output mode by writing CCS bits in TIMx_CCMRx register.
b)
Select the polarity by writing the CCxP bit in TIMx_CCER register.
Configure the used channel (1, 2 or/and 3)in PWM mode:
a)
Configure the frequency, the duty cycle and the polarity.
b)
Select the PWM 1 or 2.
3.
Configure the Channel 5 in PWM mode with the desired parameter (duty cycle).
4.
Select the Combined PWM mode by programming the GC5Cx bits.
5.
Select the Center aligned mode as counting mode.
6.
Enable the capture compare.
7.
Enable the counter.
For more details on using the timer in this mode refer to the examples provided in the
STM32Cube F3 firmware package in the Examples\TIM\TIM_Combined subfolder.
4.3
Specific features for motor control applications
4.3.1
Complementary signal and dead time feature
The STM32xx advanced timers can generate up to three complementary outputs with
insertion of dead time.
To use the complementary signal for one channel, set the two output compare enable bits of
this channel and its complementary (OCxE and OCxNE) channel.If the dead time bits are
different from zero, the two signals are generated with insertion of a dead time as illustrated
in Figure 6: Two signals are generated with insertion of a dead time:
Figure 6. Two signals are generated with insertion of a dead time
2&5()
&+
'HOD\
&+1
'HOD\
069
The dead time parameter is computed using the DTG[7:0] bits and the dead time clock
(Tdtg).
The dead time clock is computed as follows:
Tdtg = TDTS,
if DTG[7] = 0
Tdtg = 2 x TDTS,
if DTG[6] = 0
Tdtg = 8 x TDTS,
if DTG[5] = 0
Tdtg = 16 x TDTS, if DTG[7:5] = 111
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Advanced features for motor control
Where:
TDTS = TCK_INT, if CKD[1:0] = 00
TDTS = 2 x TCK_INT, if CKD[1:0] = 01
TDTS = 4 x TCK_INT, if CKD[1:0] = 10
Note:
TCK_INT is the timer internal clock.
The dead time delay is computed using the following formula:
Dead time = DTG[7:0]x Tdtg, if DTG[7] = 0
Dead time = (64+DTG[5:0]) x Tdtg, if DTG[6] = 0
Dead time = (32+DTG[4:0]) x Tdtg, if DTG[5] = 0
Dead time = (32+DTG[4:0]) x Tdtg, if DTG[7:5] = 111
For more details on using the timer in this mode refer to the examples provided in the
STM32Cube package examples in the following directories:
•
Examples\TIM\TIM_ComplementarySignals
•
Examples\TIM\TIM_Combined
Note:
This example is not available for STM32L1 Series.
4.3.2
Break input
The break input is an emergency input in the motor control application. The break function
protects power switches driven by PWM signals generated with the advanced timers. The
break input is usually connected to fault outputs of power stages and 3-phase inverters.
When activated, the break circuitry shuts down the TIM outputs and forces them to a
predefined safe state.
The break event is generated by:
•
The BRK input that has a programmable polarity and an enable bit BKE.
•
The CSS (Clock Security System).
•
Software, by setting the BG bit in the EGR register.
When a break event occurs:
•
The MOE bit (main output enable) is cleared.
•
The break status flag is set and an interrupt request can be generated.
•
Each output channel is driven with the level programmed in the OISx bit.
Break inputs in STM32L4/F7 Series and STM32F30x/F3x8 lines
In these lines there are two break inputs Break1 and Break2. The break can be generated
by any of the two BRK inputs which have:
•
a programmable polarity (BKPx bit in the TIMx_BDTR Register)
•
a programmable enable bit (BKEx in the TIMx_BDTR Register)
•
a programmable filter (BKxF[3:0] bits in the TIMx_BDTR Register) to avoid spurious
events.
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The following table presents the priorities between the two break inputs.
Table 5. Behavior of timer outputs versus Break1 and Break2 inputs
Break input 1
4.3.3
Break input 2
OCxN output
OCx output
Active
Inactive
ON after deadtime
insertion
OFF
Inactive
Active
OFF
OFF
Active
-
ON after deadtime
insertion
OFF
Locking mechanism
The advanced timers registers and bits can be protected or locked in order to safeguard the
application using the locking mechanism by programming the LOCK bits in the BDTR
register. There are three locking levels.
Table 6. Locking levels
LOCK Level 2(1)
Level 1
Register
CR2
Bits
Register
OISx
Register
OISx
CR2
OISxN
OISxN
Bits
OISx
CR2
OISxN
DTG[7:0]
DTG[7:0]
DTG[7:0]
BKE
BKE
BKE
BKP
BDTR
Bits
LOCK Level 3(2)
BDTR
AOE
BKP
AOE
BDTR
BKP
AOE
BK2E(3)
OSSR
OSSR
(3)
OSSI
OSSI
BK2P
BKF[3:0](3)
BK2F[3:0]
(3)
CCER
CCxP
CCxNP
-
-
-
-
-
-
-
-
CCER
CCMRx
CCxP
CCxNP
OCxM
OCxPE
1. LOCK Level 2 = LOCK Level 1 + CC polarity bits (CCxP/CCxNP bits in TIMx_CCER).
2. LOCK Level 3 = LOCK Level 2 + CC control bits (OCxM and OCxPE.
3. Bits present in STM32L4/F7 Series and STM32F30x/F3x8 lines.
Note:
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The LOCK bits can be written only once after the reset. Once the BDTR register has been
written, its content is frozen until the next reset.
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4.3.4
Advanced features for motor control
Specific features for feedback measurement
Encoder modes
The incremental quadrature encoder is a type of sensor used in motor-control applications
to measure the angular position and the rotation direction.
In general, the incremental quadrature encoder generates three signals: phase A, phase B
and index.
The direction of the motor depends if Phase A leads Phase B, or Phase B leads Phase A. A
third channel, Index pulse, occurs once per revolution and is used as a reference to
measure an absolute position.
The Phase A and B output signals are connected to the encoder interface to compute the
frequency and then deduce the velocity and the position. Velocity and position information
can be measured at X2 or X4 resolution. The following figures explain the encoder interface
function.
The timer's counter is incremented or decremented for each transition on both inputs TI1
and TI2.
Figure 7. Position at X4 resolution
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The timer's counter is incremented or decremented for each transition on the selected input
TI1 or TI2.
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Figure 8. Position at X2 resolution
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Note:
The counter in case of resolution X2 can also be incremented on the TI1 edge.
In STM32 timer encoder interface mode, the encoder mode3 corresponds to resolution X4.
In this mode, the counter counts up/down on both TI1 and TI2 edges.
The resolution X2 is selected when encoder mode 1 or mode 2 is selected, that is, the
counter counts up/down on TI2 edge depending on the TI1 level, or the counter counts
up/down on TI1 edge depending on TI2 level.
How to use the encoder interface
An external incremental quadrature encoder can be connected directly to the MCU without
external interface logic. The third encoder output (index) which indicates the mechanical
zero position, may be connected to an external interrupt input and trigger a counter reset.
The output signal of the incremental encoder is filtered by the STM32 timer input filter block
to reject all noise sources that typically occur in motor systems. This filter is used as
described in Section 2.3: Timer input capture mode on page 12.
TIM configuration in encoder mode
1.
Select and configure the timer input:
•
Input selection:
•
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–
TI1 connected to TI1FP1 CC1S='01' in TIMx_CCMR1 register.
–
TI2 connected to TI2FP2 CC2S='01' in TIMx_CCMR1 register.
Input polarity:
–
CC1P='0' and CC1NP='0'(CCER register, TI1FP1 non-inverted, TI1FP1=TI1).
–
CC2P='0' and CC2NP='0'(CCER register, TI1FP2 non-inverted, TI1FP2= TI2).
2.
Select the encoder mode:
•
Encoder mode1 (resolution X2 on TI2): SMS=’001’ in TIMx_SMCR register.
•
Encoder mode2 (resolution X2 on TI1): SMS=’010' in TIMx_SMCR register.
•
Encoder mode3 (resolution X4 on TI1 and TI2): SMS=’011’ in TIMx_SMCR register.
3.
Enable the timer counter:
•
Set the counter enable bit, CEN='1' in TIMx_CR1 register.
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Advanced features for motor control
Hall sensor
The Hall sensor is a type of sensor based on Hall effect: when a conductor is placed in a
magnetic field, a voltage will be generated perpendicular to both the current and the
magnetic field.
There are four types of Hall sensor IC devices that provide a digital output: unipolar
switches, bipolar switches, omni polar switches, and latches. The main difference between
them is the output waveforms (pulse duration).
The digital Hall sensor provides a digital output in relation to the magnetic field to which it is
exposed. When the magnetic field increases and is greater than the BRP (magnetic field
release point value), the output will be ON. When the magnetic field decreases and is lower
than the BOP (magnetic field operate point value) the output will be OFF.
Figure 9 presents the output waveform of a typical Hall sensor.
Figure 9. Output waveform of a typical Hall sensor
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Generally, the Hall sensor is used in the three-phase motor control. Figure 10 presents the
commutation sequence.
Figure 10. Commutation sequence
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How to use the Hall sensor interface
The STM32 timers can interfaces with the Hall effect sensors via the standard inputs (CH1,
CH2 and CH3). Setting TI1S bit in the TIMx_CR2 register, allows the input filter of channel 1
to be connected to the output of a XOR gate, combining the three input pins TIMx_CH1,
TIMx_CH2 and TIMx_CH3.
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The slave mode controller is configured in reset mode; the slave input is TI1F_ED. Thus,
each time one of the 3 inputs toggles, the counter restarts counting from 0. This creates a
time base triggered by any change on the Hall inputs.
Channel 1 is configured in input capture mode, capture signal is TRC. The captured value,
which corresponds to the time, elapsed between 2 changes on the inputs, gives information
about motor speed.
TIM configuration in Hall sensor interface mode
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1.
Configure 3 timer inputs ORed to the TI1 input channel by writing the TI1S bit in
TIMx_CR2 register to '1',
2.
Program the time base: write the TIMx_ARR to the max value (the counter must
cleared by the TI1 change. Set the prescaler to get a maximum counter period longer
than the time between 2 changes on the sensors,
3.
Program channel 1 in capture mode (TRC selected): write the CC1S bits in the
TIMx_CCMR1 register to '01'. The user can also program the digital filter if needed.
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5
High-resolution timer applications
High-resolution timer applications
The high-resolution timer was designed specifically to control power conversion systems in
switch mode power supplies of lighting systems.Though it really excels in this role, it can of
course be used in other applications with high requirements for timer resolution.
The HRTIM features up to 10 outputs which can be configured in various coupled and
autonomous modes using five timing units tied to a common master for synchronization
purposes. The synchronization with other timers is also facilitated. The HRTIM is strongly
tied to ADCs and fault inputs for feedback purposes.
For more information about the high-resolution timer, read the reference manual of the
particular MCU line.
Application related information can be found in “High brightness LED dimming using the
STM32F334 Discovery kit“(AN4885) and “Buck-boost converter using the STM32F334
Discovery kit” (AN4449).
For practical examples check following STM32Cube package subfolders:
•
Projects\STM32F3348-Discovery\Examples\HRTIM_BasicPWM
•
Projects\STM32F3348-Discovery\Examples\HRTIM_BuckBoost
•
Projects\STM32F3348-Discovery\Examples\HRTIM_BuckSyncRect
•
Projects\STM32F3348-Discovery\Examples\HRTIM_DualBuck
•
Projects\STM32F3348-Discovery\Examples\HRTIM_LLC_HalfBridge
•
Projects\STM32F3348-Discovery\Examples\HRTIM_Multiphase
•
Projects\STM32F3348-Discovery\Examples\HRTIM_Snippets
•
Projects\STM32F3348-Discovery\Examples\HRTIM_TM_PFC.
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Low-power timer
6
AN4013
Low-power timer
The main difference and advantage of the LPTIM compared to any other timer peripheral in
STM32 family of microcontrollers is the ability to continue working even in stop mode and
the possibility to generate events waking the MCU from the stop mode. Depending on the
selected clock source, the runtime power consumption can be substantially lower compared
to a general purpose timer. While it can perform a similar job as a general purpose timer,
let’s focus on task that it is better suited to do.
6.1
Used as a wakeup timer
The LPTIM can be configured to periodically wake up the MCU from stop mode, for example
to refresh a display or to read a sensor. For this purpose it needs to be configured to use a
clock source that remains functional in Stop mode. It can be an LSE, an LSI oscillator or an
external clock source. An external clock source can be generated externally and fed to the
LPTIM Input1 where the LPTIM is already configured to use it (CKSEL is appropriately
configured).
To configure the timer in this mode:
1.
Configure a clock source.
2.
Code the interrupt handler, callback function and enable the LPTIM interrupt.
3.
Setup the LPTIM peripheral:
a)
Clock source selection
b)
Set timing range using prescaler
c)
Set trigger event (software or external signal)
4.
Enable and start the timer.
5.
Go to stop mode.
For more details on using the timer in this mode, refer to examples provided in the
STM32Cube package in the Examples\LPTIM\LPTIM_Timeout subfolder.
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6.2
Low-power timer
Pulse counter
In some applications the microcontroller needs to keep track of some external events, but it
is not desirable to wake it up from stop mode with each of them. In this case, the LPTIM
configured as pulse counter comes in handy. Use the timer period/compare setting to set
the number of events required to wake the microcontroller.
To configure the timer in this mode:
1.
Configure a clock source.
2.
Code the interrupt handler callback function and enable the LPTIM interrupt.
3.
Setup the LPTIM timer peripheral:
a)
Clock source and counter source selection. Only input1 can be used as a clock
source.
b)
Typical configuration selection is immediate update mode and software trigger
source.
4.
Enable and start the timer.
5.
Go to Stop mode.
For more details on using the timer in this mode, refer to the examples provided in the
STM32Cube package in the Examples\LPTIM\LPTIM_PulseCounter subfolder.
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Specific applications
AN4013
7
Specific applications
7.1
Infrared application
The STM32 general-purpose timers can be used to emulate several infrared protocol. An
example of this application is explained in the application note Implementation of
transmitters and receivers for infrared remote control protocols with STM32Cube (AN4834).
This application note describes a software solution for implementing an RC5/SIRC receiver
and transmitter using the STM32 general-purpose timers.
This solution uses a specialized feature called IRTIM for implementation of the transmitter
part. IRTIM is available on STM32F0, STM32F3 and STM32L4 microcontroller lines.
7.2
3-phase AC and PMSM control motor
The STM32 advanced and general-purpose timers with ADC and DAC are used to control
two types of 3-phase motor: AC induction motor and PMSM, with different current sensing
methodologies:
•
Isolated current sensing (also referred as sensorless solution)
•
Three shunt resistors
•
Single shunt resistor (ST patented solution)
The STM32 timers are used also in the feedback loop to interface with the different sensors
used in the different rotor position feedback:
•
Tachogenerator
•
Quadrature encoder
•
Hall sensors: 60° and 120° placement
For more details, please refer to: stm32_pmsm_foc_motorcontrol_fmlib.
7.3
Six-step mode
The six-step mode is a specific mode of STM32 advanced timers. When complementary
outputs are used on a channel, preload bits are available on the OCxM, CCxE and CCxNE
bits. The preload bits are transferred to the shadow bits at the COM (commutation event).
The user can program in advance the configuration for the next step and change the
configuration of all the channels at the same time. COM can be generated by software by
setting the COM bit in the TIMx_EGR register or by hardware (on TRGI rising edge).
An application example of the use of this mode is the control of the brush-less 3-phase DC
motor (3-phase BLDC motor).
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Specific applications
Configuring the timer to generate a six step signal to control a brush-less 3phase DC motor (3-phase BLDC motor)
•
Time base configuration: prescaler, period, clock source
•
Channels 1, 2, 3 and 4 configured in PWM mode
•
Set the capture compare preload control bit CCPC
•
Enable the commutation interrupt source
•
Use the system tick to generate time base
•
Each commutation event, the TIM configuration is updated for the next commutation
event.
For more details on using the timer in this mode, refer to the examples provided in the
STM32Cube package in the Examples\TIM\TIM_6Steps folder.
Note:
This example is not available for STM32L1 Series.
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Revision history
8
AN4013
Revision history
Table 7. Document revision history
Date
Revision
21-Feb-2012
1
Initial release.
22-Oct-2012
2
Added support for STM32F30x, STM32F31x, STM32F37x,
STM32F38x.
3
Added support for STM32F0 Series, STM32F358xC.
Replaced “basic timers” by “general-purpose” timers in the whole
document.
Updated Section 2.1.2: External clock.
UpdatedSection 2.4: Timer output compare mode.
Updated Section 2.5: Timer PWM mode.
Updated Section 7.3: Six-step mode.
4
Extended the applicability to STM32F303xDxE. Updated:
– Table 1: Applicable products
– Table 2: Simplified overview of timer availability in STM32 products
– The document title and introduction
Added references to timer examples available in STM32Cube F3
firmware package where applicable.
5
Extended coverage to STM32F7 Series, STM32L0 Series and
STM32L4 Series.
Added:
– Section 5: High-resolution timer applications.
– Section 6: Low-power timer.
Updated:
– Table 2.: Simplified overview of timer availability in STM32
products.
– Table 3: Timer features overview.
– Section 2.4: Timer output compare mode.
12-Feb-2014
28-Jan-2015
15-Apr-2016
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Changes
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