ST72P314J2T View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
ST72P314J2T
STMicroelectronics
'ST72P314J2T' PDF : 153 Pages View PDF
ST72334J/N, ST72314J/N, ST72124J
MULTI-OSCILLATOR (Cont’d)
External RC Oscillator
This oscillator allows a low cost solution for the
main clock of the ST7 using only an external resis-
tor and an external capacitor (see Figure 21). The
selection of the external RC oscillator has to be
done by OPTION BYTE.
The frequency of the external RC oscillator (in the
range of some MHz.) is fixed by the resistor and
the capacitor values:
fOSC ~
4
REX . CEX
1)
The previous formula shows that in this MO mode,
the accuracy of the clock is directly linked to the
accuracy of the discrete components.
Figure 21. MO External RC
ST7
OSC1
OSC2
REX
CEX
Internal RC Oscillator
The Internal RC oscillator mode is based on the
same principle as the External RC oscillator in-
cluding the resistance and the capacitance of the
device. This mode is the most cost effective one
with the drawback of a lower frequency accuracy.
Its frequency is in the range of several MHz.
In this mode, the two oscillator pins have to be tied
to ground as shown in Figure 22.
The selection of the internal RC oscillator has to
be done by OPTION BYTE.
Figure 22. MO Internal RC
ST 7
OSC1
OSC2
Note:
1) This formula provides an approximation of the frequency with typical REX and CEX values at VDD=5V.
It is given only as design guidelines.
31/125
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