ST52T440F3M6 STMicroelectronics, ST52T440F3M6 Datasheet - Page 58

• Manufacturer Part Number: ST52T440F3M6
• Description: MCU 8-Bit ST52 CISC 8KB EPROM 5V 20-Pin SO
• Manufacturer: STMicroelectronics

Specifications of ST52T440F3M6

• Package: 20SO
• Family Name: ST52
• Maximum Speed: 20 MHz
• Ram Size: 256 Byte
• Program Memory Size: 8 KB
• Operating Supply Voltage: 5 V
• Data Bus Width: 8 Bit
• Program Memory Type: EPROM
• Number Of Programmable I/os: 13
• On-chip Adc: 6-chx12-bit
• Operating Temperature: -40 to 85 °C
• Number Of Timers: 1

ST52T400/T440/E440/T441
Figure 9.4 PWM Mode with Auto Reload
The 16-bit Prescaler divides the master clock,
CLKM or the external signal TCLK. The Prescaler
output can be selected setting the PRESC bit of
REG_CONF6.
NOTE: The external clock signal, applied on
TCLK pin, must have a frequency that is at least
two times smaller than the internal master clock.
When the Counter reaches the Peripheral Regis-
ter PWM_COUNT value (Compare Value), the
TIMEROUT signal changes from high to low level,
up to the next counter start.
The period of the PWM signal is obtained by using
the following formula:
T= (255-PWM_RELOAD)*TMRCLK
where TMRCLK is the output of the 16-bit pres-
caler. The duty cycle of the PWM signal is
controlled by the Output Register PWM_COUNT:
Ton =(PWM_COUNT- PWM_RELOAD)* TMRCLK
If the Output Register PWM_COUNT value is 255
the TIMEROUT signal is always at high level.
If the Output Register PWM_COUNT is 0, or less
than the PWM_RELOAD value, TIMEROUT sig-
nal is always at low level.
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compare
value
reload
register
Output
PWM
255
0
Ton
T
NOTE. If the PWM_RELOAD value increases, the
duty cycle resolution decreases.
By using a 20 MHz Master Clock a PWM fre-
quency in the range between 1.2 Hz to 78.43 Khz
may be obtained.
NOTE: The Timer, before using a new value of the
counter or of the reload, has to complete the previ-
ous counting. If the counter/reload value is
changed during counting, the new value of the
timer counter is used only at the end of the previ-
ous counting phase. This happens both in Timer
and in PWM mode.
WARNING: loading new values of the reload in
the PWM_x_RELOAD registers, the PWM/Timer is
immediately set on-fly. This can cause some side
effects during the current counting cycle. The next
cycles work normally. This occurs both in Timer
and in PWM mode.
When the Timer is in Reset, or when the device is
reset, the TOUT pin goes to threestate: it is rec-
ommended to use a pull-up or a pull-down resistor
if this output is used to drive an external device.
t
t