MC80F0304/08/16
112
November 4, 2011 Ver 2.12
21. POWER FAIL PROCESSOR
The MC80F0304/0308/0316 has an on-chip power fail detection
circuitry to immunize against power noise. A configuration reg-
ister, PFDR, can enable or disable the power fail detect circuitry.
Whenever V
DD
falls close to or below power fail voltage for
100ns, the power fail situation may reset or freeze MCU accord-
ing to PFDM bit of PFDR. Refer to “Figure 21-1 Power Fail Volt-
age Detector Register” on page 112.
In the in-circuit emulator, power fail function is not implemented
and user can not experiment with it. Therefore, after final devel-
opment of user program, this function may be experimented or
evaluated.
Figure 21-1 Power Fail Voltage Detector Register
Figure 21-2 Example S/W of Reset flow by Power fail
PFDM
7
6
5
4
3
2
1
0
PFDS
INITIAL VALUE: ---- -000
B
ADDRESS: 0F7
H
PFDR
R/W
R/W
R/W
PFDEN
PFD Operation Mode
0 : MCU will be frozen by power fail detection
1 : MCU will be reset by power fail detection
PFD Enable Bit
0: Power fail detection disable
1: Power fail detection enable
Power Fail Status
0: Normal operate
1: Set to “1” if power fail is detected
* Cautions :
Be sure to set bits 3 through 7 to “0”.
-
-
-
-
-
Function
Execution
Initialize RAM Data
PFDS =1
NO
RESET VECTOR
Initialize All Ports
Initialize Registers
RAM Clear
YES
Skip the
initial routine
PFDS = 0