ST72651AR6 STMicroelectronics, ST72651AR6 Datasheet - Page 80

• Manufacturer Part Number: ST72651AR6
• Description: LOW-POWER, FULL-SPEED USB 8-BIT MCU WITH 32K FLASH, 5K RAM, FLASH CARD I/F, TIMER, PWM, ADC, I2C, SPI
• Manufacturer: STMicroelectronics

Specifications of ST72651AR6

• Dual Supply Management: analog voltage detector on the USB power line to enable smart power switching from USB power to battery (on E suffix devices).
• Programmable Internal Voltage Regulator For Memory Cards (2.8v To 3.5v) Supplying: Flash Card I/O lines (voltage shifting)
• 5 Usb Endpoints: 1 control endpoint
• Dtc (data Transfer Coprocessor): Universal Serial/Parallel communications interface, with software plug-ins for current and future protocol standards

ST72651AR6
16-BIT TIMER (Cont’d)
11.4.3.2 Output Compare
In this section, the index, i, may be 1 or 2 because
there are 2 output compare functions in the 16-bit
timer.
This function can be used to control an output
waveform or indicate when a period of time has
elapsed.
When a match is found between the Output Com-
pare register and the free running counter, the out-
put compare function:
Two 16-bit registers Output Compare Register 1
(OC1R) and Output Compare Register 2 (OC2R)
contain the value to be compared to the counter
register each timer clock cycle.
These registers are readable and writable and are
not affected by the timer hardware. A reset event
changes the OC
Timing resolution is one count of the free running
counter: (
Procedure:
To use the output compare function, select the fol-
lowing in the CR2 register:
– Set the OCiE bit if an output is needed then the
– Select the timer clock (CC[1:0]) (see
And select the following in the CR1 register:
– Select the OLVLi bit to applied to the OCMPi pins
– Set the OCIE bit to generate an interrupt if it is
When a match is found between OCRi register
and CR register:
– OCFi bit is set.
80/161
1
OCMPi pin is dedicated to the output compare i
signal.
Clock Control
after the match occurs.
needed.
– Assigns pins with a programmable value if the
– Sets a flag in the status register
– Generates an interrupt if enabled
OCiR
OCIE bit is set
f
CPU/
CC[1:0]
Bits).
i
R value to 8000h.
MS Byte
OCiHR
).
LS Byte
OCiLR
Table 27
Doc ID 7215 Rev 4
– The OCMPi pin takes OLVLi bit value (OCMPi
– A timer interrupt is generated if the OCIE bit is
The OC
ing application can be calculated using the follow-
ing formula:
Where:
Δ
f
PRESC
If the timer clock is an external clock, the formula
is:
Where:
Δ
f
Clearing the output compare interrupt request (i.e.
clearing the OCFi bit) is done by:
1. Reading the SR register while the OCFi bit is
2. An access (read or write) to the OCiLR register.
The following procedure is recommended to pre-
vent the OCFi bit from being set between the time
it is read and the write to the OC
– Write to the OCiHR register (further compares
– Read the SR register (first step of the clearance
– Write to the OCiLR register (enables the output
CPU
EXT
t
t
pin latch is forced low during reset).
set in the CR2 register and the I bits are cleared
in the CC register (CC).
are inhibited).
of the OCFi bit, which may be already set).
compare function and clears the OCFi bit).
set.
i
R register value required for a specific tim-
= Output compare period (in seconds)
= CPU clock frequency (in hertz)
= Timer prescaler factor (2, 4 or 8 de-
= Output compare period (in seconds)
= External timer clock frequency (in hertz)
pending on CC[1:0] bits, see
Clock Control
Δ
Δ
OCiR =
OCiR =
Δt
Bits)
Δt
*
PRESC
f
EXT
*
f
CPU
i
R register:
Table 27