M16C1N Datasheet, PDF (49/238 Pages) Renesas Technology Corp – RENESAS 16-BIT SINGLE-CHIP MICROCOMPUTER M16C FAMILY / M16C/10 SERIES

M16C/1N Group
6. Clock Generation Circuit
fMAIN
(Note 1)
Compulsory discharge when CM20=0
Pulse generation
circuit for clock
edge detection
and charge/
discharge control
Charge/discharge
circuit
CM21
Oscillation stop
detection interrupt
generating circuit
Watchdog
timer
interrupt
To the CPU
CM14
On-chip oscillator
CM22
Main clock switch control
Main clock ^{To the main clock}
division circuit
#: When XIN is supplied, this repeats charge and discharge with pulses by XIN edge detection.
When XIN is not supplied, this continues charging. When the charge exceeds a certain level,
it regards the oscillation as stopped.
Note 1: As for the fMAIN, see Figure 6.1 clock generating circuit.
Figure 6.10 Oscillation stop detection circuit
Oscillation stop detection register (Note 1)
b7 b6 b5 b4 b3 b2 b1 b0
0 00 0
Symbol
CM2
Address
000C16
When reset
0416
Bit symbol
CM20
CM21
CM22
CM23
Bit name
Oscillation stop
detection bit
Oscillation stop detection
interrupt enable bit
Main clock switch bit
Clock monitor bit (Note 5)
Function
RW
0 : The function is invalid
1 : The function is valid (Note 2) ^RW
0 : Disabled
1 : Enabled (Note 3)
RW
0 : Select XIN clock
1 : Select on-chip oscillator (Note 4)
RW
0 : XIN oscillating normally
1 : XIN stopping abnormally
RO
Reserved bit
Set to "0"
RW
Note 1: In case of writing to this register, set bit 0 of the protect register (address 000A16) to "1".
Note 2: Set to "0" before stopping the oscillation of the main clock (XIN-XOUT).
(stop mode, low power dissipation mode, on-chip oscillation mode)
An oscillation stop is detected if the oscillation of the main clock (XIN-XOUT) is stopped when the following
two conditions are satisfied: (1) the oscillation stop detection function is valid and (2) CM21=1.
Note 3: Valid when CM20=1.
Note 4: CM22 bit switches to "1" automatically if an oscillation stop is detected when both CM20 bit and CM 21 bit
are "1". CM22 bit cannot be cleared when CM23=1.
Note 5: This bit is valid when both CM20 bit is "1". Use this bit for the purpose of confirming XIN operation for
oscillation stop detection interrupt execution.
Figure 6.11 Oscillation stop detection register
Rev.1.00 Oct 20, 2004 page 37 of 222
REJ09B0007-0100Z