Countermeasure Of Noise; Oscillation Noise Protector - Abov MC80F0304 User Manual

MC80F0304/08/16

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 en-
tered into oscillator and recovery the oscillation fail. This func-
tion could be enabled or disabled by the "ONP" bit of the Device
configuration area (20FF
"ONP" option bits MASK option.
The ONP function is like below.
- Recovery the oscillation wave crushed or loss caused
XIN
HF Noise
Observer
ONPb = 0
LF_on = 1
IN_CLK = 0
XIN
XIN_NF
INT_CLK reset
INT_CLK
OFP_EN
CHG_END
CLK_CHG
f
INTERNAL
Figure 22-1 Block Diagram of ONP & OFP and Respective Wave Forms
114
) for the MC80F0304/0308/0316,
H
HF Noise
Canceller
ONP
OFP
High Frq. Noise
Noise Cancel
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 /X
IN
oscillation is stopped except by stop instruction and
the low frequency noise is entered.
OFP
1
XIN_NF
Mux
0
S
Internal
OSC
en
LF Noise
CLK_CHG
Observer
en
o/f
CK
PS10
INT_CLK 8 periods
(250ns × 8 =2us)
Low Frq. Noise or
Oscillation Fail
Clock Change Start(XIN to INT_CLK)
is shorted or opened, the main
OUT
0
CLK
Changer
1 S
INT_CLK
en
OFP
(8-Bit counter)
PS10(INT_CLK/512) 256 periods
(250ns × 512 × 256 =33 ms)
Clock Change End(INT_CLK to XIN))
November 4, 2011 Ver 2.12
F
INTERNAL
ONP
IN4(2)MCLK(XO)