MC80F0204 Datasheet, PDF (104/126 Pages) List of Unclassifed Manufacturers – 8-BIT SINGLE-CHIP MICROCONTROLLERS

MC80F0104/0204
Preliminary
22. COUNTERMEASURE OF NOISE
22.1 Oscillation Noise Protector
The Oscillation Noise Protector (ONP) is used to supply
stable internal system clock by excluding the noise which
could be entered into oscillator and recovery the oscillation
fail. This function could be enabled or disabled by the
“ONP” bit of the Device configuration area (20FF_H) for
the MC80F0204, “ONP” option bits MASK option.
The ONP function is like below.
- Recovery the oscillation wave crushed or loss caused
by high frequency noise.
- Change system clock to the internal oscillation clock
when the high frequency noise is continuing.
- Change system clock to the internal oscillation clock
when the X_IN/X_OUT is shorted or opened, the main
oscillation is stopped except by stop instruction and
the low frequency noise is entered.
XIN
HF Noise
HF Noise
Canceller
1
Mux
0S
OFP
XIN_NF
Internal
0
CLK
Changer
F_INTERNAL
Observer
OSC
1S
en
INT_CLK
ONPb = 0
LF_on = 1
IN_CLK = 0
XIN
XIN_NF
INT_CLK reset
INT_CLK
OFP_EN
CHG_END
CLK_CHG
f_INTERNAL
ONP
OFP
High Frq. Noise
Noise Cancel
LF Noise
Observer ^CLK_CHG
en
PS10
en
o/f
OFP
CK _{(8-Bit counter)}
ONP
IN4(2)MCLK(XO)
INT_CLK 8 periods
(250ns × 8 =2us)
PS10(INT_CLK/512) 256 periods
(250ns × 512 × 256 =33 ms)
Low Frq. Noise or
Oscillation Fail
Clock Change Start(XIN to INT_CLK)
Clock Change End(INT_CLK to XIN))
Figure 22-1 Block Diagram of ONP & OFP and Respective Wave Forms
100
Mar. 2005 Ver 0.2