ST62T45B STMicroelectronics, ST62T45B Datasheet - Page 18

• Manufacturer Part Number: ST62T45B
• Description: 8-BIT OTP/EPROM MCU
• Manufacturer: STMicroelectronics

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17
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. C
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 (F
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 1.625 s.
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 9. Clock Circuit Block Diagram
18/72
OSC32out
OSC32in
OSCout
OSCin
f
OSC
OSCILLATOR
OSCILLATOR
32kHz
MAIN
f
INT
L1
an C
INT
L2
) is divid-
should
(START /STOP)
EOCR bit 5
MUX
Figure 8. Oscillator Configurations
C
L1n
CRYSTAL/RES ONATOR CLOCK
OSC
EXTERNAL CLOCK
OSC
f
INT
in
ST6xxx
in
ST6xxx
OSC
OSC
: 12
: 13
NC
out
out
C
L2
POR
LCD
CONTROLLER
DRIVER
Core
Timer 1 & 2
Watchdog
ADC
VA0015A
VA0016