AT89C51RB2-3CSUM データシートの表示（PDF） - Atmel Corporation

部品番号

コンポーネント説明

メーカー

AT89C51RB2-3CSUM

8-bit Microcontroller with 16K/32K Bytes Flash

Atmel Corporation 

AT89C51RB2/RC2

Functional Block

Diagram

Figure 4. Functional Oscillator Block Diagram

Reset

Reload

Xtal1

FOSC

CKRL

Osc

Xtal2

1

8-bit

:2

0

Prescaler-Divider

1

X2

CKCON0

0

Idle

CKRL = 0xFF?

CLK

PERIPH

CLK

CPU

Peripheral Clock

CPU clock

Prescaler Divider

• A hardware RESET puts the prescaler divider in the following state:

• CKRL = FFh: FCLK CPU = FCLK PERIPH = FOSC/2 (Standard C51 feature)

• Any value between FFh down to 00h can be written by software into CKRL register

in order to divide frequency of the selected oscillator:

• CKRL = 00h: minimum frequency

FCLK CPU = FCLK PERIPH = FOSC/1020 (Standard Mode)

FCLK CPU = FCLK PERIPH = FOSC/510 (X2 Mode)

• CKRL = FFh: maximum frequency

FCLK CPU = FCLK PERIPH = FOSC/2 (Standard Mode)

FCLK CPU = FCLK PERIPH = FOSC (X2 Mode)

FCLK CPU and FCLK PERIPH

In X2 Mode, for CKRL<>0xFF:

FCPU = FCLKPERIPH = 2-----×-----(--2----5-F--5--O---–-S---C-C----K----R-----L-----)

In X1 Mode, for CKRL<>0xFF then:

FCPU = FCLKPERIPH

=

-----------------F----O----S---C-------------------

4 × (255 – CKRL)

15

4180E–8051–10/06

Share Link: