M16CSLASH1N datasheet(48/238 Pages) RENESAS

48 / 238 page

Rev.1.00

Oct 20, 2004

page 36 of 222

M16C/1N Group

6. Clock Generation Circuit

REJ09B0007-0100Z

6.6 Oscillation Stop Detection Function

The oscillation stop detection function detects abnormal stopping of the main clock by causes such as

opening and shorting of the XIN oscillation circuit. When oscillation stop is detected, an oscillation stop

detection interrupt is issued. When an oscillation stop detection interrupt is issued, the on-chip oscillator

in the microcomputer operates automatically and is used as the main clock in place of the XIN clock. This

allows interrupt processing.

The oscillation stop detection function can be enabled/disabled with bit 0 and bit 1 of the oscillation stop

detection register. When this bit is set to "112", the function is enabled. After the reset is released, the

oscillation stop detection function becomes disabled because the bit value is "002".

Table 6.5 lists the specification of oscillation stop detection function, Figure 6.10 shows a configuration

diagram of the oscillation stop detection circuit and Figure 6.11 shows the configuration of the oscillation

stop detection register.

Table 6.5 Specification overview of the oscillation stop detection function

Item

Specification

Oscillation stop detectable clock and

XIN ≥ 2 MHz

frequency bandwidth

Enabling condition for oscillation stop

When the oscillation stop detection bit (bit 0 at address 000C16)

detection function

and the oscillation stop detection interrupt enable bit (bit 1 at

address 000C16) are set to "1"

Operation at oscillation stop detection

• Oscillation stop detection interrupt occurs

Notes on STOP mode, low power

Before stopping the main clock (XIN-XOUT), set the

dissipation mode, and on-chip

oscillation stop detection enable bit to "0" to disable the

oscillator mode

oscillation stop detection function. Enable main clock

(XIN-XOUT) oscillation and after the oscillation stabilizes,

set the bit to "1" again.

Notes on WAIT mode

If the peripheral function clock is stopped in WAIT mode

with the WAIT mode peripheral function clock stop bit

(bit 2 at address 000616), oscillation stop will be detected.

Do not stop the peripheral function clock in WAIT mode.

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