Reset Initial Conditions - Holtek HT66F20-1 Manual

Reset Initial Conditions

The different types of reset described affect the reset flags in different ways. These flags, known
as PDF and TO are located in the status register and are controlled by various microcontroller
operations, such as the SLEEP or IDLE Mode function or Watchdog Timer. The reset flags are
shown in the table:
TO
0
u
1
1
The following table indicates the way in which the various components of the microcontroller are
affected after a power-on reset occurs.
Item
P�og�a� Counte�
Inte��upts
WDT
Ti�e�/Event Counte�
Input/Output Po�ts
Stack Pointe�
The different kinds of resets all affect the internal registers of the microcontroller in different ways.
To ensure reliable continuation of normal program execution after a reset occurs, it is important to
know what condition the microcontroller is in after a particular reset occurs. The following table
describes how each type of reset affects each of the microcontroller internal registers. Note that
where more than one package type exists the table will reflect the situation for the larger package
type.
HT66F20-1
Register
(Power-on)
MP0 x x x x x x x x
MP1 x x x x x x x x
BP - - - - - - - 0
ACC x x x x x x x x
PCL 0 0 0 0 0 0 0 0
TBLP x x x x x x x x
TBLH x x x x x x x x
TBHP - - - - - - x x
STATUS - - 0 0 x x x x
SMOD 0 0 0 0 0 0 11
LVDC - - 0 0 - 0 0 0
I�TEG - - - - 0 0 0 0
WDTC 0 1 1 1 1 0 1 0
TBC 0 0 1 1 0 1 1 1
I�TC0 - 0 0 0 0 0 0 0
I�TC1 0 0 0 0 0 0 0 0
I�TC� 0 0 0 0 0 0 0 0
MFI0 - - 0 0 - - 0 0
Rev. 1.40
HT66F20-1/HT66F30-1/HT68F20-1/HT68F30-1
PDF
0 Powe�-on �eset
u RES o� LVR �eset du�ing �ORMAL o� SLOW Mode ope�ation
u WDT ti�e-out �eset du�ing �ORMAL o� SLOW Mode ope�ation
1 WDT ti�e-out �eset du�ing IDLE o� SLEEP Mode ope�ation
Reset to ze�o
All inte��upts will �e disa�led
Clea� afte� �eset� WDT �egins counting
Ti�e� Counte� will �e tu�ned off
I/O po�ts will �e setup as inputs� and A�0~A�7 is as A/D input pin.
Stack Pointe� will point to the top of the stack
Reset
RES or LVR Reset
u u u u u u u u
u u u u u u u u
- - - - - - - 0
u u u u u u u u
0 0 0 0 0 0 0 0
u u u u u u u u
u u u u u u u u
- - - - - - u u
- - u u u u u u
0 0 0 0 0 0 11
- - 0 0 - 0 0 0
- - - - 0 0 0 0
0 1 1 1 1 0 1 0
0 0 1 1 0 1 1 1
- 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0
- - 0 0 - - 0 0
�4
Flash MCU with EEPROM
RESET Conditions
"u" stands fo� unchanged
Condition After RESET
WDT Time-out WDT Time-out
(Normal Operation)
u u u u u u u u u u u u u u u u
u u u u u u u u u u u u u u u u
- - - - - - - 0 - - - - - - - u
u u u u u u u u u u u u u u u u
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
u u u u u u u u u u u u u u u u
u u u u u u u u u u u u u u u u
- - - - - - u u - - - - - - u u
- - 1 u u u u u - - 1 1 u u u u
0 0 0 0 0 0 11 u u u u u u u u
- - 0 0 - 0 0 0 - - u u - u u u
- - - - 0 0 0 0 - - - - u u u u
0 1 1 1 1 0 1 0 u u u u u u u u
0 0 1 1 0 1 1 1 u u u u u u u u
- 0 0 0 0 0 0 0 - u u u u u u u
0 0 0 0 0 0 0 0 u u u u u u u u
0 0 0 0 0 0 0 0 u u u u u u u u
- - 0 0 - - 0 0 - - u u - - u u
�ove��e� ��� �01�
(IDLE)