7549 datasheet(53/84 Pages) RENESAS

53 / 84 page

Rev.2.01

Oct 15, 2007

Page 53 of 81

REJ03B0202-0201

7549 Group

Fig 68. State transition of oscillation stop detection circuit

Notes on switch of clock

(1) Executing the state transition after stabilizing XIN oscillation.

(2) MCU cannot be returned by on-chip oscillator and its operation is stopped since internal reset does not

occur at oscillation stop detected in state 2'a. Accordingly, do not execute the transition to state 2'a.

(3) STP instruction cannot be used when oscillation stop detection circuit is in active.

(4) The same applies when the high-speed on-chip oscillator is set as

φSOURCE. Make sure that the low-speed

on-chip oscillator should also oscillate. When a reset occurs, the high-speed on-chip oscillator stops.

Reset state 1

Oscillation stop detection reset disabled

When oscillation stop is detected;

CLKSTP2 is set to “1”.

Internal RESET does not occur.

= 02

= 12

CLKSTP0 = 02

(CLKSTP2 is set to “0”.)

CLKSTP 0 = 12

(Note 1)

Oscillation stop is detected

(internal reset)

Reset state 2

External reset (RESET=“L”)

⋅ Power-on reset

⋅ Low voltage detection reset

⋅ Watchdog timer reset

⋅ Reset by STP instruction function

Return from oscillation stop detection reset

CLKSTP2 is set to “1”.

So, return from oscillation stop reset can be

confirmed.

CLKSTP1= 02

CLKSTP1 = 02

(CLKSTP2 is

set to “0”.)

CLKM54 = 102

CLKM54 = 002

(Note 1)

Prohibitive state

MCU stops when oscillation stops

occurs.

State 3'a

State 2'b

State 3'b

State 3'c

Oscillation stop detection reset enabled

When oscillation stop is detected;

CLKSTP2 is set to “1”.

Internal RESET occurs.

Oscillation stop detection reset enabled

When oscillation stop is detected;

CLKSTP2 is set to “1”.

Internal RESET occurs.

Reset

released

CLKM54 = 102

CLKM54 = 002

(Note 1)

CLKM54=102

CLKM54=002

(Note 1)

State 3

XIN oscillation

: enabled

Low-speed on-chip oscillator : enabled

State 3'

XIN oscillation

: enabled

Low-speed on-chip oscillator : enabled

XIN

: enabled

High-speed on-chip oscillator : stop

Low-speed on-chip oscillator : enabled

CLKSTP1

CLKSTP1 = 12

State 2'

CLKSTP1= 12

XIN

: enabled

High-speed on-chip oscillator : stop

Low-speed on-chip oscillator : enabled

Reset

released

XIN oscillation

: enabled

Low-speed on-chip oscillator : enabled

XIN oscillation

: enabled

Low-speed on-chip oscillator : enabled

State 2

(Note 2)

φSOURCE: XIN

φSOURCE: Low-speed on-chip oscillator (Note 4)

Oscillation stop detection

circuit is in active. (Note 3)

State 2'a (Note 2)

Oscillation stop detection reset disabled

When oscillation stop is detected;

CLKSTP2 is set to "1".

Internal RESET does not occur.

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