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8. Clock Generation Circuits
Figure 8.2
CM0 Register
b7 b6 b5 b4
b1
b2
b3
System Clock Control Register 0(1)
Symbol
CM0
Address
0006h
Bit Symbol
Bit Name
RW
CM00
After Reset
0000 1000b
RW
NOTES:
1. Set the CM0 register after the PRC0 bit in the PRCR register is set to 1 (write enable).
2. The followings are regarding memory expansion mode:
When the PM07 bit in the PM0 register is set to 0 (BCLK output), set bits CM01 and CM00 to 00b.
When bits PM15 and PM14 in the PM1 register are set to 01b (ALE output to P5_3), set bits CM01 and CM00 to 00b.
When bits CM01 and CM00 are set to 00b while the PM07 bit is set to 1 (function selected in bits CM01 and CM00), port P5_3
outputs an "L" signal (port P5_3 does not function as an I/O port).
3. fC32 does not stop running.
4. To set the CM04 bit is set to 1, set the PU25 bit in the PUR2 register to 0 (no pull-up) while bits PD8_7 and PD8_6 in the PD8
register are set to 00b (port P8_6 and P8_7 in input mode).
5. The CM05 bit stops the main clock running to enter low-power consumption mode or on-chip oscillator low-power consumption
mode. The CM05 bit cannot detect whether the main clock stops or not. To stop the main clock running, set the CM05 bit to 1
after the CM07 bit is set to 1 with a stable sub clock oscillation or after the CM21 bit in the CM2 register is set to 1 (on-chip
oscillator clock).
When the CM05 bit is set to 1, XOUT becomes "H". The built-in feedback resistor remains ON. XIN is pulled up to XOUT via the
feedback resistor.
6. When the CM05 bit is set to 1, bits MCD4 to MCD0 in the MCD register become 01000b (divide-by-8 mode). In on-chip oscillator
mode, bits MCD4 to MCD0 do not become 01000b even if the CM05 bit is set to 1.
7. Once the CM06 bit is set to 1, it cannot be set to 0 by program.
8. After the CM04 bit is set to 1 and the sub clock oscillation stabilizes, change the CM07 bit setting from 0 to 1.
After the CM05 bit is set to 0 and the main clock oscillation stabilizes, change the CM07 bit setting from 1 to 0.
Do not change the CM07 bit simultaneously with the CM04 bit or the CM05 bit.
9. If the PM21 bit in the PM2 register is set to 1 (disables a clock change), bits CM02, CM05, and CM07 do not change when
written.
10. To set the PM21 bit to 1, set the PM21 bit to 1 after setting the CM07 bit.
11. When stop mode is entered, the CM03 bit becomes 1.
b0
Function
b1 b0
0 0: I/O port P5_3
0 1: Outputs fC
1 0: Outputs f8
1 1: Outputs f32
Clock output function select bits(2)
CM01
CM02
In wait mode, peripheral
function clock stop bit(9)
0: Peripheral clock does not stop in wait mode
1: Peripheral clock stops in wait mode(3)
CM03
XCIN-XCOUT drive capacity
select bit(11)
0: Low
1: High
CM04
Port XC switch bit
0: I/O port function
1: XCIN-XCOUT oscillation function(4)
CM05
Main clock (XIN-XOUT)
stop bit(5, 9)
0: Main clock oscillates
1: Main clock stops(6)
CM06
Watchdog timer
function select bit
CPU clock select bit 0(8, 9, 10)
0: Watchdog timer interrupt
1: Reset(7)
CM07
0: Clock, selected by the CM21 bit, divided by
the MCD register
1: Sub clock
RW