39
3851 Group
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
MITSUBISHI MICROCOMPUTERS
Fig. 48 State transitions of system clock
CM
4
: Port Xc switch bit
0 : I/O port function (stop oscillating)
1 : X
CIN
-X
COUT
oscillating function
CM
5
: Main clock (X
IN
- X
OUT
) stop bit
0 : Operating
1 : Stopped
CM
7
, CM
6
: Main clock division ratio selection bit
b7 b6
0 0 :
φ
= f(X
IN
)/2 ( High-speed mode)
0 1 :
φ
= f(X
IN
)/8 (Middle-speed mode)
1 0 :
φ
= f(X
CIN
)/2 (Low-speed mode)
1 1 : Not available
Notes
Reset
C
4
“
←
“
CM
“0
←→
“1
CM
“1
←→
“0
CM
4
“1
←→
“0
CM
6
“1
←→
“0
C
7
“
←
“
C
4
“
←
“
C
5
“
←
“
CM
6
“1”
←→
“0”
CM
6
“1”
←→
“0”
CPU mode register
(CPUM : address 003B
16
)
b7
b4
CM
“0
←→
“1
CM
“1
←→
“0
CM
7
=0
CM
6
=1
CM
5
=0(8 MHz oscillating)
CM
4
=0(32 kHz stopped)
Middle-speed mode
(f(
φ
)=1 MHz)
CM
7
=0
CM
6
=1
CM
5
=0(8 MHz oscillating)
CM
4
=1(32 kHz oscillating)
Middle-speed mode
(f(
φ
)=1 MHz)
CM
7
=0
CM
6
=0
CM
5
=0(8 MHz oscillating)
CM
4
=0(32 kHz stopped)
High-speed mode
(f(
φ
)=4 MHz)
CM
7
=1
CM
6
=0
CM
5
=0(8 MHz oscillating)
CM
4
=1(32 kHz oscillating)
Low-speed mode
(f(
φ
)=16 kHz)
CM
7
=1
CM
6
=0
CM
5
=1(8 MHz stopped)
CM
4
=1(32 kHz oscillating)
Low-speed mode
(f(
φ
)=16 kHz)
CM
7
=0
CM
6
=0
CM
5
=0(8 MHz oscillating)
CM
4
=1(32 kHz oscillating)
High-speed mode
(f(
φ
)=4 MHz)
1 :
Switch the mode by the allows shown between the mode blocks. (Do not switch between the modes directly without an allow.)
2 :
The all modes can be switched to the stop mode or the wait mode and return to the source mode when the stop mode or the wait mode is
ended.
3 :
Timer operates in the wait mode.
4 :
When the stop mode is ended, a delay of approximately 1 ms occurs by connecting prescaler 12 in middle/high-speed mode.
5 :
When the stop mode is ended, a delay of approximately 16 ms occurs by Timer 1 and Timer 2 in low-speed mode.
6 :
Wait until oscillation stabilizes after oscillating the main clock X
IN
before the switching from the low-speed mode to middle/high-speed
mode.
7 :
The example assumes that 8 MHz is being applied to the X
IN
pin and 32 kHz to the X
CIN
pin.
φ
indicates the internal clock.