3820 GROUP USER’S MANUAL
1-40
MITSUBISHI MICROCOMPUTERS
3820 Group
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
Register contents
(0001
16
)
Timer Y (low-order)
Port P0 direction register
Port P1 direction register
Port P2 direction register
PULL register B
Timer Y (high-order)
Serial I/O1 control register
UART control register
Serial I/O2 control register
Timer X (high-order)
(1 )
( 2)
(3 )
(4 )
(5)
(6 )
(7)
(8)
(9)
(10)
(11)
(12)
(13)
(14)
(15)
(16)
(17)
(18)
(19)
(20)
(21)
(22)
(23)
(24)
(0003
16
)
(0005
16
)
(0017
16
)
(001A
16
)
(001B
16
)
(001D
16
)
(0020
16
)
(0021
16
)
(0022
16
)
(0023
16
)
(0024
16
)
(0025
16
)
(0026
16
)
(0027
16
)
(0028
16
)
(0029
16
)
(002A
16
)
Address
Timer X (low-order)
Timer 1
Timer 2
Timer 3
Timer X mode register
Timer Y mode register
Timer 123 mode register
φ
output control register
00
16
00
16
00
16
FF
16
01
16
FF
16
FF
16
FF
16
FF
16
FF
16
00
16
00
16
00
16
Port P7 direction register
(000F
16
)
00
16
1 1
1 0 0 0
0
0
Serial I/O1 status register
(0019
16
) 1 0
0 0 0 0
0
0
Port P4 direction register
Port P5 direction register
Port P6 direction register
(0009
16
)
(000B
16
)
(000D
16
)
00
16
00
16
00
16
00
16
00
16
00
16
(25)
(26)
(27)
(0037
16
)
(0038
16
)
(0039
16
)
Watchdog timer control register
Segment output enable register
LCD mode register
00
16
PULL register A
(0016
16
) 0 0
0 0 1 0
1
1
Note.
: Undefined
The contents of all other registers and RAM are undefined
at poweron reset, so they must be initialized by software.
(28)
(29)
(30)
(31)
(32)
(33)
(34)
(35)
(003A
16
)
(003B
16
)
(003C
16
)
(003D
16
)
(003E
16
)
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
00
16
00
16
00
16
00
16
0 1
0 0 1 0
0
0
00
16
Contents of address FFFC
16
1
(PS)
(PC
H
)
(PC
L
)
Contents of address FFFD
16
(003F
16
)
00
16
0 1
1 1 1 1
1
1
00
16
RESET CIRCUIT
To reset the microcomputer, RESET pin should be held at an “L”
level for 2
μ
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 X
IN
clock time to stabilize, internal operation does
not begin until after 8200 X
IN
clock cycles (timer 1 and timer 2 are
connected together and 512 cycles of f(X
IN
)/16) are complete. Af-
ter the reset is completed, the program starts from the address
contained in address FFFD
16
(high-order byte) and address
FFFC
16
(low-order byte).
Make sure that the reset input voltage is less than 0.5 V for V
CC
of
2.5 V (Extended operating temperature version: the reset input
voltage is less than 0.6V for V
CC
of 3.0V).
Fig. 40 Internal state of microcomputer immediately after re-
set
Fig. 39 Example of reset circuit
(Note)
0.2V
CC
0V
0V
Note. Reset release voltage : V
= 2.5V
(Extended operating temperature version : 3.0V)
Power on
V
CC
RESET
V
CC
RESET
Power source voltage
detection circuit
Reset input
voltage
Power source