M16C65 Datasheet, PDF (158/829 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
8.7.2 Operation When CM27 Bit is 1 (Oscillation Stop, Re-Oscillation Detect Interrupt)
When the CM20 bit is 1 (oscillation stop/re-oscillation detect function enabled), the system is placed in
the state shown in Table 8.7 if the main clock detects oscillation stop or re-oscillation.
The CM21 bit is automatically set to 1 in high-speed, medium-speed, or low-speed mode. The FRA01
bit does not change. Thus, high-speed and medium-speed mode become 125 kHz on-chip oscillator
mode or 40 MHz on-chip oscillator mode. Because the CM07 bit does not change, low-speed mode
remains in low-speed mode, but clock sources for the peripheral functions become fOCO-S or fOCO-F.
When the CM21 bit is set to 1, the CM14 bit is set to 0 (125 kHz on-chip oscillator on), but the FRA00
bit remains unchanged (40 MHz on-chip oscillator does not oscillate automatically). Thus, when the
FRA01 bit is set to 1 (40 MHz on-chip oscillator selected), set the FRA00 bit to 1 (40 MHz on-chip
oscillator on). Do not set the FRA00 bit to 0 while the FRA01 bit is 1, and vice versa.
Since the CM21 bit remains unchanged in PLL operating mode, select 125 kHz on-chip oscillator mode
or 40 MHz on-chip oscillator mode inside the interrupt routine.
Table 8.7 State after Oscillation Stop and Re-Oscillation Detect When CM27 Bit is 1
Condition
After Detection
Main clock High-speed mode
oscillation Medium-speed
stop detected mode
Low-speed mode
40 MHz on-chip
oscillator mode
• Oscillation stop, re-oscillation detection interrupt is generated
• CM14 bit is 0 (125 kHz on-chip oscillator on)
• CM21 bit is 1 (fOCO-S or fOCO-F is used as the clock source for
the CPU and peripheral function clocks) ^{(1), (2)}
• CM22 bit is 1 (main clock stop detected)
• CM23 bit is 1 (main clock stopped)
125 kHz on-chip
oscillator mode
PLL operating mode • Oscillation stop, re-oscillation detection interrupt is generated
• CM14 bit is 0 (125 kHz on-chip oscillator on)
• CM21 bit remains unchanged
• CM22 bit is 1 (main clock stop detected)
• CM23 bit is 1 (main clock stopped)
Main clock -
re-oscillation
detected
• Oscillation stop, re-oscillation detection interrupt is generated
• CM14 bit is 0 (125 kHz on-chip oscillator on)
• CM21 bit remains unchanged
• CM22 bit is 1 (main clock stop detected)
• CM23 bit is 0 (main clock oscillating)
Notes:
1. fOCO-S or fOCO-F is selected depending on the FRA01 bit status.
2. fC is used as the CPU clock in low-speed mode.
REJ09B0484-0030 Rev.0.30 Sep 09, 2008
Page 123 of 791