M37544 RENESAS [Renesas Technology Corp], M37544 Datasheet - Page 12

• Manufacturer Part Number: M37544
• Description: SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
• Manufacturer: RENESAS [Renesas Technology Corp]

Rev.1.04
REJ03B0012-0104Z
7544 Group
[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. 12 Switching method of CPU mode register
2004.06.08
selection bits (bits 6 and 7 of CPUM)
Wait by on-chip 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
page 12 of 66
Main routine
16
.
Select 1/1, 1/2, 1/8 or on-chip oscillator.
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
an on-chip oscillator meets the requirement).
Start with an on-chip 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. 11 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
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”.)
b0
CPU mode register
(CPUM: address 003B
Processor mode bits (Note 1)
Stack page selection bit
On-chip oscillator oscillation control bit
X
Oscillation mode selection bit (Note 1)
Clock division ratio selection bits
IN
b1 b0
b7 b6
0
0
1
1
0
0
1
1
0 : 0 page
1 : 1 page
0 : On-chip oscillator oscillation enabled
1 : On-chip oscillator oscillation stop
0 : Ceramic/quartz-crystal or RC oscillation enabled
1 : Ceramic/quartz-crystal or RC oscillation stop
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 on-chip oscillator
1 : f( ) = f(X
Not available
/quartz-crystal
16
IN
IN
IN
, initial value: 80
)/2 (High-speed mode)
)/8 (Middle-speed mode)
) (Double-speed mode)(Note 2)
oscillation is selected.
16
)