MG82FX564AE Datasheet, PDF (115/151 Pages) Megawin Technology Co., Ltd – Dual data pointer

19. Reset
During reset, all I/O Registers are set to their initial values, the port pins are weakly pulled to VDD, and the
program starts execution from the Reset Vector, 0000H, or ISP start address by Hardware Option setting. The
MG82Fx564 has six sources of reset: power-on reset, WDT reset, software reset, external reset, brown-out reset
and illegal address reset.
19.1. Reset Source
There are six reset sources in MG82Fx564 to generate an internal reset to initial CPU and registers. Figure 19-1
shows the reset source diagram.
Figure 19-1. Reset Source Diagram
Power-On Reset
Brown-Out Reset
External Reset
WDT Reset
Software Reset or
Illegal Addr Reset
Illegal Addr Reset
POF
BORF
EXRF
WRF
SWRF
IARF
Internal Reset
19.2. Power-On Reset
Power-on reset (POR) is used to internally reset the CPU during power-up. The CPU will keep in reset state and
will not start to work until the VDD power rises above the voltage of Power-On Reset. And, the reset state is
activated again whenever the VDD power falls below the POR voltage. During a power cycle, VDD must fall
below the POR voltage before power is reapplied in order to ensure a power-on reset
PCON0: Power Control Register 0
SFR Page
= All
SFR Address = 0x87
7
6
5
SMOD1 SMOD0
GF
R/W
R/W
R/W
POR = 0001-0000, RESET = 000X-0000
4
3
2
1
0
POF
GF1
GF0
PD
IDL
R/W
R/W
R/W
R/W
R/W
Bit 4: POF, Power-On Flag.
0: The flag must be cleared by software to recognize next reset type.
1: Set by hardware when VDD rises from 0 to its nominal voltage. POF can also be set by software.
The Power-on Flag, POF, is set to ―1‖ by hardware during power up or when VDD power drops below the POR
voltage. It can be clear by firmware and is not affected by any warm reset such as external reset, Brown-Out
reset, software reset (ISPCR.5) and WDT reset. It helps users to check if the running of the CPU begins from
power up or not. Note that the POF must be cleared by firmware.
MEGAWIN
MG82FEL564 Data Sheet
115