SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
MITSUBISHI MICROCOMPUTERS
3825 Group
1-36
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 immediately after re-
set
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
Note : The contents of all other registers and RAM are undefined after
reset, so they must be initialized by software.
! : Undefined
Register contents
Address
0 0 0 0 16
0 0 0 2 16
0 0 0 3 16
0 0 0 4 16
0 0 0 5 16
0 0 0 6 16
0 0 0 8 16
0 0 0 9 16
0 0 0 A 16
0 0 0 B 16
0 0 0 C 16
0 0 0 D 16
0 0 0 E 16
0 0 0 F 16
0 0 1 0 16
0 0 1 1 16
0 0 1 6 16
0 0 1 7 16
0 0 1 9 16
0 0 1 A 16
0 0 1 B 16
0 0 2 0 16
0 0 2 1 16
0 0 2 2 16
0 0 2 3 16
0 0 2 4 16
0 0 2 5 16
0 0 2 6 16
0 0 2 7 16
0 0 2 8 16
0 0 2 9 16
0 0 2 A 16
0 0 3 4 16
0 0 3 8 16
0 0 3 9 16
0 0 3 A 16
0 0 3 B 16
0 0 3 C 16
0 0 3 D 16
0 0 3 E 16
0 0 3 F 16
( P S )
( P C H )
( P C L )
(10)
(11)
(12)
(13)
(14)
(15)
(16)
(17)
(18)
(19)
(20)
(21)
(22)
(23)
(24)
(25)
(26)
(27)
(28)
(29)
(30)
(31)
(32)
(33)
(34)
( 1 )
( 2 )
( 3 )
( 4 )
( 5 )
( 6 )
( 7 )
( 8 )
( 9 )
(35)
(36)
(37)
(38)
(39)
(40)
(41)
(42)
(43)
Timer Y (low)
Port P5 direction register
Port P6
Port P6 direction register
PULL register B
Timer Y (high)
Serial I/O control register
UART control register
Timer X (high)
Timer X (low)
Timer X mode register
Timer Y mode register
Timer 123 mode register
Serial I/O status register
Port P7
Port P7 direction register
Port P8
A-D control register
Segment output enable register
LCD mode register
PULL register A
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
Port P5
Port P4 direction register
Port P4
Port P3
Port P2 direction register
Port P2
Port P1 output control register
Port P1
Port P0
Port P8 direction register
Timer 1
Timer 2
Timer 3
Clock output control register
111 0 00
0
100 0 00
0
000 0 1 0
0
1 0 0 1 00
0
!
1
!
!! !
! !
0016
FF16
0116
FF16
0016
Contents of address FFFD 16
Contents of address FFFC 16