M16C29 Datasheet, PDF (73/499 Pages) Renesas Technology Corp – RENESAS MCU M16C FAMILY / M16C/Tiny SERIES

M16C/29 Group
7. Clock Generation Circuit
System Clock Control Register 0 ⁽¹⁾
b7 b6 b5 b4 b3 b2 b1 b0
Symbol
CM0
Address
000616
After Reset
010010002
Bit Symbol
Bit Name
Function
RW
CM00 ^{Clock output function}
See Table 7.3
RW
select bit
CM01
RW
CM02
CM03
CM04
CM05
CM06
CM07
Wait Mode peripheral function 0: Do not stop peripheral function clock in wait mode
clock stop bit ⁽¹⁰⁾
1: Stop peripheral function clock in wait mode ⁽⁸⁾
RW
XCIN-XCOUT drive capacity 0: LOW
select bit ⁽²⁾
1: HIGH
RW
Port XC select bit ⁽²⁾
0: I/O port P8 6, P87
1: XCIN-XCOUT generation function⁽⁹⁾
RW
Main clock stop bit
(3, 10, 12, 13)
0: On ⁽⁴⁾
1: Off ⁽⁵⁾
RW
Main clock division select 0: CM16 and CM17 valid
bit 0 ^{(7, 13, 14)}
1: Division by 8 mode
RW
System clock select bit
(6, 10, 11, 12)
0: Main clock, PLL clock, or on-chip oscillator clock
1: Sub-clock
RW
NOTES:
1. Write to this register after setting the PRC0 bit in the PRCR register to 1 (write enable).
2. The CM03 bit is set to 1 (high) when the CM04 bit is set to 0 (I/O port) or the MCU goes to a stop mode.
3. This bit is provided to stop the main clock when the low power dissipation mode or on-chip oscillator low power dissipation mode
is selected. This bit cannot be used for detection as to whether the main clock stopped or not. To stop the main clock, the
following setting is required:
(1) Set the CM07 bit to 1 (Sub-clock select) or the CM21 bit in the CM2 register to 1 (on-chip oscillator select) with the sub-
clock stably oscillating.
(2) Set the CM20 bit in the CM2 register to 0 (Oscillation stop, re-oscillation detection function disabled).
(3) Set the CM05 bit to 1 (Stop).
4. During external clock input, set the CM05 bit to 0 (On).
5. When CM05 bit is set to 1, the XOUT pin goes "H". Futhermore, because the internal feedback resistor remains connectes,
the XIN pin is pulled "H" to the same level as XOUT via the feedback resistor.
6. After setting the CM04 bit to 1 (XCIN-XCOUT oscillator function), wait until the sub-clock oscillates stably before switching
the CM07 bit from 0 to 1 (sub-clock).
7. When entering stop mode from high or middle speed mode, on-chip oscillator mode or on-chip oscillator low power mode, the
CM06 bit is set to 1 (divided-by-8 mode).
8. The fC32 clock does not stop. During low speed or low power dissipation mode, do not set this bit to 1(peripheral clock turned
off in wait mode).
9. To use a sub-clock, set this bit to 1. Also, make sure ports P86 and P87 are directed for input, with no pull-ups.
10. When the PM21 bit in the PM2 register is set to 1 (clock modification disable), writing to bits CM02, CM05, and CM07 has
no effect.
11. If the PM21 bit needs to be set to 1, set the CM07 bit to 0 (main clock) before setting it.
12. To use the main clock a the clock source for the CPU clock, follow the procedure below.
(1) Set the CM05 bit to 0 (oscillate).
(2) Wait the main clock oscillation stabilized.
(3) Set all bits CM11, CM21, and CM07 to 0.
13. When the CM21 bit is set to 0 (on-chip oscillaor turned off) and the CM05 bit is set to 1 (main clock turned off), the CM06 bit
is fixed to 1 (divide-by-8 mode) and the CM15 bit is fixed to 1 (drive capability High).
14. To return from on-chip oscillator mode to high-speed or middle-speed mode set both bits CM06 and CM15 to 1.
Figure 7.2 CM0 Register
Rev. 1.12 Mar.30, 2007
REJ09B0101-0112
page 49 of 458