LC872G08A/06A/04A

No.A1400-4/27

Oscillation Circuits

• Internal oscillation circuits

Low-speed RC oscillation circuit :

For system clock (100kHz)

Medium-speed RC oscillation circuit :

For system clock (1MHz)

Multifrequency RC oscillation circuit :

For system clock (8MHz)

• External oscillation circuits

Hi-speed CF oscillation circuit:

For system clock, with internal Rf

Low speed crystal oscillation circuit:

For low-speed system clock, with internal Rf

1) The CF and crystal oscillation circuits share the same pins. The active circuit is selected under program control.

2) Both the CF and crystal oscillator circuits stop operation on a system reset. When the reset is released, only the

CF oscillation circuit resumes operation.

System Clock Divider Function

• Can run on low current.

• The minimum instruction cycle selectable from 300ns, 600ns, 1.2μs, 2.4μs, 4.8μs, 9.6μs, 19.2μs, 38.4μs, and

76.8

μs (at a main clock rate of 10MHz).

Internal Reset Function

• Power-on reset (POR) function

1) POR reset is generated only at power-on time.

2) The POR release level can be selected from 8 levels (1.67V, 1.97V, 2.07V, 2.37V, 2.57V, 2.87V, 3.86V, and

4.35V) through option configuration.

• Low-voltage detection reset (LVD) function

1) LVD and POR functions are combined to generate resets when power is turned on and when power voltage falls

below a certain level.

2) The use/disuse of the LVD function and the low voltage threshold level (7 levels: 1.91V, 2.01V, 2.31V, 2.51V,

2.81V, 3.79V, 4.28V).

Standby Function

• HALT mode: Halts instruction execution while allowing the peripheral circuits to continue operation.

1) Oscillation is not halted automatically.

• HOLD mode: Suspends instruction execution and the operation of the peripheral circuits.

1) The CF, RC, and crystal oscillators automatically stop operation.

2) There are four ways of resetting the HOLD mode.

(1) Setting the reset pin to the lower level.

(2) System resetting by watchdog timer or low-voltage detection

(3) Having an interrupt source established at either INT0, INT1, INT2 or INT4

* INT0 and INT1 HOLD mode reset is available only when level detection is set.

(4) Having an interrupt source established at port 0.

• X'tal HOLD mode: Suspends instruction execution and the operation of the peripheral circuits except the base timer.

1) The RC oscillator automatically stop operation.

2) The state of crystal oscillations established when the X'tal HOLD mode is entered is retained.

3) There are five ways of resetting the X'tal HOLD mode.

(1) Setting the reset pin to the low level.

(2) System resetting by watchdog timer or low-voltage detection.

(3) Having an interrupt source established at either INT0, INT1, INT2 or INT4

* INT0 and INT1 HOLD mode reset is available only when level detection is set.

(4) Having an interrupt source established at port 0.

(5) Having an interrupt source established in the base timer circuit.

Note: Available only when X’tal oscillation is selected.