m30262f8gp Renesas Electronics Corporation., m30262f8gp Datasheet - Page 41

• Manufacturer Part Number: m30262f8gp
• Description: Renesas 16-bit Cmos Single-chip Microcomputer M16c Family / M16c/20 Series
• Manufacturer: Renesas Electronics Corporation.

Oscillation Stop Detection
Figure 1.8.6. Oscillation stop detection register
Oscillation stop detection register (Note 1)
Note 1: Write to this register after setting bit PRC0, of register PRCR, to "1" (write enable).
Note 2: CM21 is set to "1" (ring oscillator clock) when the main clock is stopped, and the following conditions exist:
Note 3: If CM20 is "1", and CM23 is "1" (main clock turned off), do not set CM21 to "0".
Note 4: This bit is set to "1" by main clock stop detection and re-oscillation detection. Each oscillation stop, re-oscillation
Note 5: Read CM23 in an oscillation stop, re-oscillation detection interrupt handling routine to determine the main
Note 6: Effective when bit CM07, of register CM0, is "0".
Note 7: When bit PM21, of register PM2, is "1" (clock modification disabled), writing to CM20 has no effect.
Note 8: Set CM20 to "0" (disable) before entering stop mode. After exiting stop mode, set CM20 back to "1" (enable).
Note 9: Set CM20 to "0" (disable) before setting bit CM05, of register CM0.
Note 10: CM20, CM21, and CM27 do not change at oscillation stop detection reset.
b7 b6 b5 b4 b3
0 0
• CM20 is "1" (oscillation stop, re-oscillation detection function enabled).
• CM27 is "1" (oscillation stop, re-oscillation detection interrupt).
• CPU clock source is the main clock.
detection interrupt must correspond to a "0" to "1" transition of CM22. Once an interrupt is received, the bit can
only be cleared via an explicit "0" write operation. Otherwise, further interrupts will be disabled. Only "0" writes can
affect the bit value. CM22 is also used as a means for distinguishing between those interrupts caused by the
oscillation stop, re-oscillation detection circuitry, and those initiated by the watchdog timer.
clock status.
Preliminary Specifications Rev. 0.9
Specifications in this manual are tentative and subject to change.
b2 b1 b0
Bit symbol
Nothing is assigned. Writes must set to "0". Reads are indeterminate.
Reserved bit
CM20
CM21
CM22
CM23
CM27
Symbol
CM2
Operation select bit
(when an oscillation stop,
re-oscillation is detected)
(Note 10)
Oscillation stop, re-
oscillation detection bit
(Notes 7, 8, 9, 10)
Oscillation stop, re-
oscillation detection flag
(Note 4)
X
CPU clock switch bit
(Notes 2, 3, 6, 10)
Renesas Technology Corp.
IN
monitor flag (Note 5)
Bit name
Address
000C
16
0 : Oscillation stop, re-oscillation
1 : Oscillation stop, re-oscillation
0 : Main clock oscillating
1 : Main clock turned off
When reset
0 : Main clock (Ring oscillator
1 : Ring oscillator clock
0 : Reset
1 : Oscillation stop, re-oscillation
Must always be set to "0".
0 : Main clock stop, re-oscillation
1 : Main clock stop, re-oscillation
0X000000
detection function is disabled.
detection function enabled.
detection interrupt
turned off
(Ring oscillator oscillating)
not detected
detected
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
2
Function
(Note 10)
M16C/26 Group
R W
35