GMS81C2020 Datasheet, PDF (82/92 Pages) Hynix Semiconductor – CMOS Single-Chip 8-Bit Microcontroller with A/D Converter & VFD Driver

GMS81C2020/GMS81C2120
Hyundai Micro Electro nics
23. POWER FAIL PROCESSOR
The GMS81C2020 and GMS81C2120 has an on-chip
power fail detection circuitry to immunize against power
noise. A configuration register, PFDR, can enable (if clear/
programmed) or disable (if set) the Power-fail Detect cir-
cuitry. If VDD falls below 2.4~3.0V range for longer than
50 nS, the Power fail situation may reset MCU according
to PFDM bit of PFDR.
As below PFDR register is not implemented on the in-cir-
cuit emulator, user can not experiment with it. Therefore,
after final development of user program, this function may
be experimented.
Note: Power fail processor function is not available on 3V
operation, because this function will detect power
fail all the time.
PFDR
Power Fail Detector Register
-
-
-
-
Reserved
PFDIS PFDM
PFS
ADDRESS : EFH
RESET VALUE : -----100
Power Fail Status
0 : Normal Operate
1 : This bit force to "1" when
Power fail was detected
Operation Mode
0 : Normal operation regardless
of power fail
1 : MCU will be reset during power fail
Disable Flag
0 : Power fail detection enable
1 : Power fail detection disable
Figure 23-1 Power Fail Detector Register
RESET VECTOR
PFS =1
YES
NO
RAM CLEAR
INITIALIZE RAM DATA
INITIALIZE ALL PORTS
INITIALIZE REGISTERS
Skip the
initial routine
FUNTION
EXECUTION
Figure 23-2 Example S/W of RESET by Power fail
82
preliminary
Nov. 1999 Ver 0.0