Technical information
27
MITSUBISHI MICROCOMPUTERS
3806 Group
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
Reset Circuit
______
To reset the microcomputer, the RESET pin should be held at an
______
“L” level for 2 µs or more. Then the RESET pin is returned to an
“H” level (Note 1), reset is released. Internal operation does not
begin until after 8 to 13 XIN clock cycles are completed. After the
reset is completed, the program starts from the address contained
in address FFFD16 (high-order byte) and address FFFC16 (low-or-
der byte).
Make sure that the reset input voltage is less than 0.8 V for VCC of
4.0 V (Note 2).
Note 1. The power source voltage should be between the follow-
ing voltage.
• Between 3.0 V and 5.5 V for standard version
• Between 4.0 V and 5.5 V for extended operating tem-
perature version
• Between 2.7 V and 5.5 V for high-speed version
Note 2. Reset input voltage is less than the following voltage.
• 0.6 V for VCC = 3.0 V
• 0.8 V for VCC = 4.0 V
• 0.54 V for VCC = 2.7 V
Fig. 23 Internal status of microcomputer after reset
Fig. 22 Example of reset circuit
4.0V
0.8V
0V
0V
V
CC
RESET
Power source
voltage
Reset input
voltage
V
SS
M51953AL
4
5
1
3
0.1 µ F
3806 group
Note.
✕
: Undefined
✽ : The initial values of CM
1
are determined by the level at the
CNV
SS
pin.
The contents of all other registers and RAM are undefined
after a reset, so they must be initialized by software.
Register contents
(0001
16
) • • •
Timer 2
Port P0 direction register
Port P1 direction register
Port P2 direction register
Port P3 direction register
Port P4 direction register
Port P5 direction register
Port P6 direction register
Port P7 direction register
Port P8 direction register
Timer XY mode register
Serial I/O1 status register
Serial I/O1 control register
UART control register
Serial I/O2 control register
Timer 1
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
(10)
(11)
(12)
(13)
(14)
(15)
(16)
(17)
(18)
(19)
(20)
(21)
(22)
(23)
(24)
(25)
(26)
(27)
(28)
(29)
(30)
(31)
(32)
(0003
16
) • • •
(0005
16
) • • •
(0007
16
) • • •
(0009
16
) • • •
(000B
16
) • • •
(000D
16
) • • •
(000F
16
) • • •
(0011
16
) • • •
(0019
16
) • • •
(001A
16
) • • •
(001B
16
) • • •
(001D
16
) • • •
(0020
16
) • • •
(0021
16
) • • •
(0022
16
) • • •
(0023
16
) • • •
(0024
16
) • • •
(0025
16
) • • •
(0026
16
) • • •
(0027
16
) • • •
(0034
16
) • • •
(0036
16
) • • •
(0037
16
) • • •
(003A
16
) • • •
(003B
16
) • • •
(003C
16
) • • •
(003D
16
) • • •
(003E
16
) • • •
Address
Prescaler 12
Prescaler X
Timer X
Prescaler Y
Timer Y
AD/DA control register
D-A1 conversion register
D-A2 conversion register
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
000000 0
✽
00
16
00
16
00
16
000010 00
FF
16
FF
16
FF
16
FF
16
00
16
FF
16
01
16
FF
16
00
16
00
16
00
16
00
16
00
16
111000 00
100000 00
00
16
00
16
00
16
Contents of address FFFC
16
✕✕✕✕✕
1
✕✕
(PS)
(PC
H
)
(PC
L
)
Contents of address FFFD
16
00
16
00
16
00
16
(003F
16
) • • •