AT89LP213 datasheet(12/90 Pages) ATMEL

12 / 90 page

3538A–MICRO–7/06

AT89LP213/214 [Preliminary]

System Clock

The system clock is generated directly from one of three selectable clock sources. The three

sources are the on-chip crystal oscillator, external clock source, and internal RC oscillator. The

clock source is selected by the Clock Source User Fuses as shown in Table 9-1. No internal

clock division is used to generate the CPU clock from the system clock. See “User Configuration

Fuses” on page 71.

9.1

Crystal Oscillator

When enabled, the internal inverting oscillator amplifier is connected between XTAL1 and

XTAL2 for connection to an external quartz crystal or ceramic resonator. When using the crystal

oscillator, P3.2 and P3.3 will have their inputs and outputs disabled. When using the crystal

oscillator, XTAL2 should not be used to drive a board-level clock without a buffer.

9.2

External Clock Source

The external clock option disables the oscillator amplifier and allows XTAL1 to be driven directly

by the clock source. XTAL2 may be left unconnected, used as P3.3 I/O, or configured to output

a divided version of the system clock.

9.3

Internal RC Oscillator

The AT89LP213/214 has an internal RC oscillator tuned to 8.0 MHz ±2.5%. When enabled as

the clock source, XTAL1 and XTAL2 may be used as P3.2 and P3.3 respectively. XTAL2 may

also be configured to output a divided version of the system clock. The frequency of the oscilla-

tor may be adjusted by changing the RC Adjust Fuses. (See “User Configuration Fuses” on

page 71).

9.4

System Clock Out

When the AT89LP213/214 is configured to use either an external clock or the internal RC oscil-

lator, a divided version of the system clock may be output on XTAL2 (P3.3). The Clock Out

feature is enabled by setting the COE bit in CLKREG. The two CDV bits determine the clock

divide ratio. For example, setting COE = “1” and CDIV = “00” when using the internal oscillator

will result in a 3.950 MHz (±5%) clock output on P3.3. P3.3 must be configured as an output in

order to use the clock out feature.

Table 9-1.

Clock Source Settings

Clock Source

Fuse 1

Clock Source

Fuse 0

Selected Clock Source

Crystal Oscillator

Reserved

External Clock on XTAL1

Internal 8 MHz RC Oscillator

AT89LP213 Datasheet(PDF) 12 Page - ATMEL Corporation

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