ST7FL15F1MAE STMICROELECTRONICS [STMicroelectronics], ST7FL15F1MAE Datasheet - Page 54

• Manufacturer Part Number: ST7FL15F1MAE
• Description: 8-bit MCU for automotive with single voltage Flash/ROM memory, data EEPROM, ADC, 5 timers, SPI
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

ST7L15, ST7L19
DUAL 12-BIT AUTORELOAD TIMER 4 (cont’d)
11.2.3 Functional Description
11.2.3.1 PWM Mode
This mode allows up to four Pulse Width Modulat-
ed signals to be generated on the PWMx output
pins.
PWM Frequency
The four PWM signals can have the same fre-
quency (f
cies. This is selected by the ENCNTR2 bit which
enables single timer or dual timer mode (see
ure 32
The frequency is controlled by the counter period
and the ATR register value. In dual timer mode,
PWM2 and PWM3 can be generated with a differ-
ent frequency controlled by CNTR2 and ATR2.
Following the above formula,
– If f
– If f
Notes:
1. The maximum value of ATR is 4094 because it
must be lower than the DC4R value, which in this
case must be 4095.
2. To update the DCRx registers at 32 MHz, the
following precautions must be taken:
– if the PWM frequency is < 1 MHz and the TRANx
– if the PWM frequency is > 1 MHz, the TRANx bit
Duty Cycle
The duty cycle is selected by programming the
DCRx registers. These are preload registers. The
DCRx values are transferred in Active duty cycle
registers after an overflow event if the correspond-
ing transfer bit (TRANx bit) is set.
The TRAN1 bit controls the PWMx outputs driven
by Counter 1 and the TRAN2 bit controls the
PWMx outputs driven by Counter 2.
PWM generation and output compare are done by
comparing these active DCRx values with the
counter.
54/138
1
f
minimum value is 1 kHz (ATR register value = 0).
f
minimum value is 8 kHz (ATR register value = 0).
bit is set asynchronously, it should be set twice
after a write to the DCRx registers.
should be set along with FORCEx bit with the
same instruction (use a load instruction and not
two bset instructions).
PWM
PWM
COUNTER
COUNTER
and
is 2 MHz (ATR register value = 4094),the
is 8 MHz (ATR register value = 4092), the
f
PWM
PWM
Figure
) or can have two different frequen-
is 4 MHz
is 32 MHz
= f
COUNTER
33).
,
the maximum value of
,
the maximum value of
/ (4096 - ATR)
Fig-
The maximum available resolution for the PWMx
duty cycle is:
where ATR is equal to 0. With this maximum reso-
lution, 0% and 100% duty cycle can be obtained
by changing the polarity.
At reset, the counter starts counting from 0.
When an upcounter overflow occurs (OVF event),
the preloaded Duty cycle values are transferred to
the active Duty Cycle registers and the PWMx sig-
nals are set to a high level. When the upcounter
matches the active DCRx value, the PWMx sig-
nals are set to a low level. To obtain a signal on a
PWMx pin, the contents of the corresponding ac-
tive DCRx register must be greater than the con-
tents of the ATR register.
Note for ROM devices only: The PWM can be
enabled/disabled only in overflow ISR, otherwise
the first pulse of PWM can be different from ex-
pected one because no force overflow function is
present.
The maximum value of ATR is 4094 because it
must be lower than the DCR value, which in this
case must be 4095.
Polarity Inversion
The polarity bits can be used to invert any of the
four output signals. The inversion is synchronized
with the counter overflow if the corresponding
transfer bit in the ATCSR2 register is set (reset
value). See
Figure 34. PWM Polarity Inversion
The Data Flip Flop (DFF) applies the polarity inver-
sion when triggered by the counter overflow input.
Output Control
The PWMx output signals can be enabled or disa-
bled using the OEx bits in the PWMCR register.
ATCSR2 Register
PWMxCSR Register
PWMx
TRANx
OPx
Resolution = 1 / (4096 - ATR)
Figure
overflow
counter
34.
DFF
inverter
PWMx
PIN