ST6285 View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
'ST6285' PDF : 76 Pages View PDF
ST62T85B/E85B
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 ma-
chine 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
CRYSTA L/RESONATOR CLOCK
ST6xxx
OSCin
OSCout
CL1n
CL2
VA0016
EXTERNAL CLOCK
ST6xxx
OSCin
OSCout
NC
VA0015A
Figure 9. Clock Circuit Block Diagram
fOSC
OSCin
fINT
MAIN
OSCILLAT OR
OSCout
POR
: 13
Core
Timer 1 & 2
& Artimer
fINT
: 12
Watchdog
ADC
LCD
CONTROLLER
DRIVER
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