m38039mf-xxxsp Mitsumi Electronics, Corp., m38039mf-xxxsp Datasheet - Page 15

• Manufacturer Part Number: m38039mf-xxxsp
• Description: Single-chip 8-bit Cmos Microcomputer
• Manufacturer: Mitsumi Electronics, Corp.

MISRG
(1) Bit 0 of address 0010
When the MCU stops the clock oscillation by the STP instruction
and the STP instruction has been released by an external interrupt
source, usually, the fixed values of Timer 1 and Prescaler 12
(Timer 1 = 01
in order for the oscillation to stabilize. The user can inhibit the au-
tomatic setting by setting “1” to bit 0 of MISRG (address 0010
However, by setting this bit to “1”, the previous values, set just be-
fore the STP instruction was executed, will remain in Timer 1 and
Prescaler 12. Therefore, you will need to set an appropriate value
to each register, in accordance with the oscillation stabilizing time,
before executing the STP instruction.
Figure 12 shows the structure of MISRG.
(2) Bits 1, 2, 3 of address 0010
In order to switch the clock mode of an MCU which has a sub-
clock, the following procedure is necessary:
set CPU mode register (003B
wait for oscillation stabilization --> switch to middle-speed mode
(or high-speed mode).
However, the 3803/3804 group has the built-in function which au-
tomatically switches from low to middle-speed mode either by the
SCL/SDA interrupt (only for the 3804 group) or by program.
Fig.12 Structure of MISRG
matic Switch Function
ter STP instruction released bit
16
, Prescaler 12 = FF
b7
N o t e s 1: D u r i n g o p e r a t i o n i n l o w - s p e e d m o d e , i t i s p o s s i b l e a u t o m a t i c a l l y t o
16:
16
Oscillation stabilizing time set af-
2 : W h e n a u t o m a t i c s w i t c h t o m i d d l e - s p e e d m o d e f r o m l o w - s p e e d m o d e
) --> start main clock oscillation -->
16:
s w i t c h t o m i d d l e - s p e e d m o d e o w i n g t o S C L / S D A i n t e r r u p t . T h i s i s
v a l i d o n l y f o r t h e 3 8 0 4 g r o u p .
o c c u r s , t h e v a l u e s o f C P U m o d e r e g i s t e r ( 3 B
16
) are automatically reloaded
Middle-speed Mode Auto-
b0
M I S R G
( M I S R G : a d d r e s s 0 0 1 0
O s c i l l a t i o n s t a b i l i z i n g t i m e s e t a f t e r S T P i n s t r u c t i o n
r e l e a s e d b i t
M i d d l e - s p e e d m o d e a u t o m a t i c s w i t c h s e t b i t
M i d d l e - s p e e d m o d e a u t o m a t i c s w i t c h w a i t t i m e s e t b i t
M i d d l e - s p e e d m o d e a u t o m a t i c s w i t c h s t a r t b i t
( D e p e n d i n g o n p r o g r a m )
N o t u s e d ( r e t u r n “ 0 ” w h e n r e a d )
( D o n o t w r i t e “ 1 ” t o t h i s b i t )
0: Automatically set “01
1: Automatically set disabled
0: Not set automatically
1: Automatic switching enabled (Notes 1, 2)
0: 4.5 to 5.5 machine cycles
1: 6.5 to 7.5 machine cycles
0: Invalid
1: Automatic switch start (Note 2)
“FF
16
).
16
” to Prescaler 12
The SCL/SDA interrupt source enables an automatic switch when
the middle-speed mode automatic switch set bit (bit 1) of MISRG
(address 0010
switch execution depend on the settings of bits 5 and 6 of the I
start/stop condition control register (address 0016
SCL/SDA interrupt pin polarity selection bit and bit 6 is the SCL/
SDA interrupt pin selection bit. The main clock oscillation stabiliz-
ing time can also be selected by middle-speed mode automatic
switch wait time set bit (bit 2) of the MISRG.
The middle-speed mode can also be automatically switched by
program while operating in low-speed mode. By setting the
middle-speed automatic switch start bit (bit 3) of MISRG (address
0010
matic switch set bit is “1” while operating in low-speed mode, the
MCU will automatically switch to middle-speed mode. In this case,
the oscillation stabilizing time of the main clock can be selected by
the middle-speed automatic switch wait time set bit (bit 2) of
MISRG (address 0010
(only for 3804 group)
3803 group)
Middle-speed mode automatic switch by SCL/SDA Interrupt
Middle-speed mode automatic switch by program(for 3804/
16
) to “1” in the condition that the middle-speed mode auto-
1 6
)
16
1 6
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
” to Timer 1,
) c h a n g e .
16
) is set to “1”. The conditions for an automatic
MITSUBISHI MICROCOMPUTERS
16
).
3803/3804 Group
16
). Bit 5 is the
2
15
C