M16C62A Datasheet, PDF (30/242 Pages) Mitsubishi Electric Semiconductor – SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER

Clock Generating Circuit
Mitsubishi microcomputers
M16C / 62A Group (80-pin)
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
Figure 1.9.4 shows the system clock control registers 0 and 1.
System clock control register 0 (Note 1)
b7 b6 b5 b4 b3 b2 b1 b0
Symbol
CM0
Address
000616
When reset
4816
Bit symbol
CM00
CM01
CM02
CM03
Bit name
Function
RW
Clock output function
select bit
(Valid only in single-chip
mode)
b1 b0
0 0 : I/O port P57
0 1 : fC output
1 0 : f8 output
1 1 : f32 output
WAIT peripheral function 0 : Do not stop peripheral function clock in wait mode
clock stop bit
1 : Stop peripheral function clock in wait mode (Note 8)
XCIN-XCOUT drive capacity 0 : LOW
select bit (Note 2)
1 : HIGH
CM04
CM05
Port XC select bit
Main clock (XIN-XOUT)
stop bit (Note 3, 4, 5)
0 : I/O port
1 : XCIN-XCOUT generation (Note 9)
0 : On
1 : Off
CM06
Main clock division select 0 : CM16 and CM17 valid
bit 0 (Note 7)
1 : Division by 8 mode
CM07
System clock select bit
(Note 6)
0 : XIN, XOUT
1 : XCIN, XCOUT
Note 1: Set bit 0 of the protect register (address 000A16) to “1” before writing to this register.
Note 2: Changes to “1” when shiffing to stop mode and at a reset.
Note 3: When entering low power dissipation mode, main clock stops by using this bit. To stop the main clock, when the
sub clock oscillation is stable, set system clock select bit (CM07) to “1” before setting this bit to “1”.
Note 4: When inputting external clock, only clock oscillation buffer is stopped and clock input is acceptable.
Note 5: If this bit is set to “1”, XOUT turns “H”. The built-in feedback resistor remains being connected, so XIN turns
pulled up to XOUT (“H”) via the feedback resistor.
Note 6: Set port XC select bit (CM04) to “1” and stabilize the sub-clock oscillating before setting this bit from “0” to “1”.
Do not write to both bits at the same time. And also, set the main clock stop bit (CM05) to “0” and stabilize the
main clock oscillating before setting this bit from “1” to “0”.
Note 7: This bit changes to “1” when shifting from high-speed/medium-speed mode to stop mode and at a reset. When
shifting from low-speed/low power dissipation mode to stop mode, the value before stop mode is retained.
Note 8: fC32 is not included. Do not set to “1” when using low-speed or low power dissipation mode.
Note 9: When the XCIN/XCOUT is used, set ports P86 and P87 as the input ports without pull-up.
System clock control register 1 (Note 1)
b7 b6 b5 b4 b3 b2 b1 b0
00 0 0
Symbol
CM1
Address
000716
When reset
2016
Bit symbol
Bit name
CM10
All clock stop control bit
(Note4)
Reserved bit
Function
0 : Clock on
1 : All clocks off (stop mode)
Must always be set to “0”
RW
Reserved bit
Must always be set to “0”
Reserved bit
Must always be set to “0”
Reserved bit
Must always be set to “0”
CM15
XIN-XOUT drive capacity
select bit (Note 2)
0 : LOW
1 : HIGH
CM16
CM17
Main clock division
select bit 1 (Note 3)
b7 b6
0 0 : No division mode
0 1 : Division by 2 mode
1 0 : Division by 4 mode
1 1 : Division by 16 mode
Note 1: Set bit 0 of the protect register (address 000A16) to “1” before writing to this register.
Note 2: This bit changes to “1” when shifting from high-speed/medium-speed mode to stop mode and at a reset. When
shifting from low-speed/low power dissipation mode to stop mode, the value before stop mode is retained.
Note 3: Can be selected when bit 6 of the system clock control register 0 (address 000616) is “0”. If “1”, division mode is
fixed at 8.
Note 4: If this bit is set to “1”, XOUT turns “H”, and the built-in feedback resistor is cut off. XCIN and XCOUT turn high-
impedance state.
Figure 1.9.4. Clock control registers 0 and 1
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