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SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
MITSUBISHI MICROCOMPUTERS
3822 Group
RESET CIRCUIT
To reset the microcomputer, RESET pin should be held at an “L”
level for 2
s or more. Then the RESET pin is returned to an “H”
level (the power source voltage should be between 2.5 V and
5.5 V, and the oscillation should be stable), reset is released. In or-
der to give the XIN clock time to stabilize, internal operation does
not begin until after 8200 XIN clock cycles (timer 1 and timer 2 are
connected together and 512 cycles of f(XIN)/16) are complete. Af-
ter the reset is completed, the program starts from the address
contained in address FFFD16 (high-order byte) and address
FFFC16 (low-order byte).
Make sure that the reset input voltage is less than 0.5 V for VCC of
2.5 V (Extended operating temperature version: the reset input
voltage is less than 0.6V for VCC of 3.0V).
Fig. 36 Internal state of microcomputer after reset
Fig. 35 Example of reset circuit
(Note)
0.2VCC
0V
Note. Reset release voltage : VCC = 2.5V
(Extended operating temperature version : 3.0V)
Power on
VCC
RESET
VCC
RESET
Power source voltage
detection circuit
Reset input
voltage
Power source
voltage
Register contents
(000116)
Timer Y (low)
Port P0 direction register
Port P1 direction register
Port P2 direction register
PULL register B
Timer Y (high)
Serial I/O control register
UART control register
Timer X (high)
(10)
(11)
(12)
(13)
(14)
(15)
(16)
(17)
(18)
(19)
(20)
(21)
(22)
(23)
(24)
(000316)
(000516)
(001716)
(001A16)
(001B16)
(002016)
(002116)
(002216)
(002316)
(002416)
(002516)
(002616)
(002716)
(002816)
(002916)
(002A16)
Address
Timer X (low)
Timer 1
Timer 2
Timer 3
Timer X mode register
Timer Y mode register
Timer 123 mode register
φ output control register
0016
(000F16)
1 1 10 00
0
Serial I/O status register (001916) 1 0 00 00
0
Port P4 direction register
Port P5 direction register
Port P6 direction register
(000916)
(000B16)
(000D16)
(25)
(26)
(27)
(003416)
(003816)
(003916)
A-D control register
Segment output enable register
LCD mode register
PULL register A
(001616) 0 0 00 10
1
Note ! : Undefined
The contents of all other registers and RAM are undefined
after reset, so they must be initialized by software.
(28)
(29)
(30)
(31)
(32)
(33)
(34)
(003A16)
(003B16)
(003C16)
(003D16)
(003E16)
Interrupt edge selection register
CPU mode register
Interrupt request register 1
Interrupt request register 2
Interrupt control register 1
Interrupt control register 2
Processor status register
Program counter
1 0 0 1 00
0
Contents of address FFFC 16
!
(PS)
(PCH)
(PCL)
Contents of address FFFD 16
(003F16)
0 0 0010
0
0016
( 1 )
( 2 )
( 3 )
( 4 )
( 5 )
( 6 )
( 7 )
( 8 )
( 9 )
0
1
!
!!
! !
FF16
0116
FF16
0016
Port P7 direction register