M16C65 Datasheet, PDF (156/829 Pages) Renesas Technology Corp – RENESAS MCU M16C FAMILY / M16C/60

Under development
M16C/65 Group
Preliminary Specification
This is a preliminary specification and is subject to change.
8. Clock Generator
8.5 Clock Output Function
In single-chip mode, the f1, f8, f32 or fC clock can be output from the CLKOUT pin. Use bits CM01 to
CM00 in the CM0 register, and the PCLK5 bit in the PCLKR register to select the clock. f8 has the same
frequency as f1 divided by 8, and f32 has the same frequency as f1 divided by 32.
Set the frequency of a clock output from the CLKOUT pin to 25 MHz or below.
8.6 System Clock Protection Function
The system clock protection function prohibits the CPU clock from changing clock sources when the main
clock is selected as the CPU clock source. This is to prevent the CPU clock from stopping due to an
unexpected program operation.
When the PM21 bit in the PM2 register is set to 1 (clock change disabled), the following bits remain
unchanged even if they are written to.
• The CM02 bit in the CM0 register (peripheral function clock f1 in wait mode)
• The CM05 bit in the CM0 register (to prevent the main clock from being stopped)
• The CM07 bit in the CM0 register (clock source of the CPU clock)
• The CM10 bit in the CM1 register (stop mode is not entered)
• The CM11 bit in the CM1 register (clock source of the CPU clock)
• The CM20 bit in the CM2 register (oscillation stop/re-oscillation detect function set)
• All bits in the PLC0 register (PLL frequency synthesizer set)
To use the system clock protect function, set the CM05 bit in the CM0 register to 0 (main clock oscillation)
and CM07 bit to 0 (main clock as CPU clock source), and then follow the procedures below.
(1)Set the PRC1 bit in the PRCR register to 1 (write to PM2 register enabled).
(2)Set the PM21 bit in the PM2 register to 1 (clock change disabled).
(3)Set the PRC1 bit in the PRCR register to 0 (write to PM2 register disabled).
When the PM21 bit is 1, do not execute the WAIT instruction.
REJ09B0484-0030 Rev.0.30 Sep 09, 2008
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