M16CSLASH1N datasheet(49/238 Pages) RENESAS

49 / 238 page

Rev.1.00

Oct 20, 2004

page 37 of 222

M16C/1N Group

6. Clock Generation Circuit

REJ09B0007-0100Z

CM20

CM21

CM22

CM23

Main clock switch bit

Oscillation stop detection

interrupt enable bit

Oscillation stop

detection bit

Clock monitor bit (Note 5)

Reserved bit

Set to "0"

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.

b7 b6 b5 b4 b3 b2 b1 b0

0 : XIN oscillating normally

1 : XIN stopping abnormally

0 : Select XIN clock

1 : Select on-chip oscillator (Note 4)

0 : Disabled

1 : Enabled (Note 3)

0 : The function is invalid

1 : The function is valid (Note 2)

Oscillation stop detection register (Note 1)

Symbol

CM2

Address

000C16

When reset

0416

Function

Bit name

Bit symbol

Figure 6.11 Oscillation stop detection register

fMAIN

CM22

CM21

Oscillation stop

detection interrupt

generating circuit

Charge/discharge

circuit

On-chip oscillator

To the CPU

Watchdog

timer

interrupt

Main clock

Main clock switch control

To the main clock

division circuit

Compulsory discharge when CM20=0

Pulse generation

circuit for clock

edge detection

and charge/

discharge control

CM14

(Note 1)

#: 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

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