M37544G Mitsubishi Electric, M37544G Datasheet - Page 10

• Manufacturer Part Number: M37544G
• Description: Single-Chip 8-Bit CMOS Microcomputer
• Manufacturer: Mitsubishi Electric

[CPU mode register] CPUM
The CPU mode register contains the stack page selection bit.
This register is allocated at address 003B
Switching method of CPU mode register
Switch the CPU mode register (CPUM) at the head of program af-
ter releasing Reset in the following method.
Fig. 10 Switching method of CPU mode register
10
selection bits (bits 6 and 7 of CPUM)
Wait by ring oscillator operation until
establishment of oscillator clock
Switch the clock division ratio
selection bit (bit 5 of CPUM)
Switch the oscillation mode
After releasing reset
Main routine
16
.
When using a ceramic / quartz-crystal oscillation, wait
until establlishment of oscillation from oscillation starts.
When using an RC oscillation, wait time is not required
basically (time to execute the instruction to switch from
a ring oscillator meets the requirement).
Select 1/1, 1/2, 1/8 or ring oscillator.
Start with a built-in ring oscillator
An initial value is set as a ceramic / quartz-crystal
oscillation mode. When it is switched to an RC
oscillation, its oscillation starts.
Fig. 9 Structure of CPU mode register
b7
Note 1: The bit can be rewritten only once after releasing reset. After rewriting
2: These bits are used only when a ceramic / quartz-crystal oscillation is selected.
Do not use these when an RC oscillation is selected.
it is disable to write any data to the bit. However, by reset the bit is
initialized and can be rewritten, again.
(It is not disable to write any data to the bit for emulator MCU
“M37544RSS”.)
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
MITSUBISHI MICROCOMPUTERS
b0
CPU mode register
(CPUM: address 003B
Processor mode bits (Note 1)
Ring oscillator oscillation control bit
Clock division ratio selection bits
Stack page selection bit
X
Oscillation mode selection bit (Note 1)
IN
b1 b0
b7 b6
0
0
1
1
0 : 0 page
1 : 1 page
0 : Ring oscillator oscillation enabled
1 : Ring oscillator oscillation stop
0 : Ceramic / quartz-crystal or RC oscillation enabled
1 : Ceramic / quartz-crystal or RC oscillation stop
0
0
1
1
0 : Ceramic / quartz-crystal oscillation
1 : RC oscillation
oscillation control bit
0 Single-chip mode
1
0
1
0 : f( ) = f(X
1 : f( ) = f(X
0 : applied from ring oscillator
1 : f( ) = f(X
Not available
16
IN
IN
IN
)/2 (High-speed mode)
)/8 (Middle-speed mode)
, initial value: 80
) (Double-speed mode)(Note 2)
7544 Group
16
)