ST62P45BQ1/XXX View Datasheet(PDF) - STMicroelectronics
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ST62P45BQ1/XXX Datasheet PDF : 72 Pages
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ST62T45B/E45B
3 CLOCKS, RESET, INTERRUPTS AND POWER SAVING MODES
3.1 CLOCK SYSTEM
3.1.1 Main Oscillator
The MCU features a Main Oscillator which can be
driven by an external clock, or used in conjunction
with an AT-cut parallel resonant crystal or a suita-
ble ceramic resonator.
Figure 8 illustrates various possible oscillator con-
figurations using an external crystal or ceramic res-
onator, an external clock input. CL1 an CL2 should
have a capacitance in the range 12 to 22 pF for an
oscillator frequency in the 4-8 MHz range.
The internal MCU clock Frequency (FINT) is divid-
ed by 13 to drive the CPU core and by 12 to drive
the A/D converter and the watchdog timer, while
clock used to drive on-chip peripherals depends
on the peripheral as shown in the clock circuit
block diagram.
With an 8MHz oscillator frequency, the fastest
machine cycle is therefore 1.625µs.
A machine cycle is the smallest unit of time needed
to execute any operation (for instance, to increment
the Program Counter). An instruction may require
two, four, or five machine cycles for execution.
Figure 8. Oscillator Configurations
CRYSTAL/RES ONATOR CLOCK
ST6xxx
OSCin
OSCout
CL1n
CL2
VA0016
EXTERNAL CLOCK
ST6xxx
OSCin
OSCout
NC
VA0015A
Figure 9. Clock Circuit Block Diagram
fOSC
OSCin
fINT
MAIN
OSCILLATOR
OSCout
OSC32in
OSC 32out
32kHz
OSCILLATOR
MUX
EOCR bit 5
(START /STOP)
POR
: 13
Core
Timer 1 & 2
fINT
: 12
W atchdog
ADC
LCD
CONTROLLER
DRIVER
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