AT89LP51RB2 datasheet(49/254 Pages) ATMEL

49 / 254 page

3722A–MICRO–10/11

AT89LP51RB2/RC2/IC2 Preliminary

Figure 6-7.

Peripheral Clock Selection

SIX2

UART Clock. In Compatibility Mode, clear for one system clock period per peripheral clock cycle and set for two clock

periods per peripheral clock cycle (only valid when X2 = 1). In Fast Mode, clear for one system clock period and set for

TPS+1 clocks per peripheral clock cycle. This bit affects the generated baud rate during modes 0 and 2.

T2X2

Timer 2 Clock. In Compatibility Mode, clear for TPS+1 system clock periods per peripheral clock cycle and set for

2(TPS+1) clock periods per peripheral clock cycle. In Fast Mode, clear for one system clock period and set for TPS+1

clocks per peripheral clock cycle. This bit affects the timer increment/decrement rate.

T1X2

Timer 1 Clock. In Compatibility Mode, clear for TPS+1 system clock periods per peripheral clock cycle and set for

2(TPS+1) clock periods per peripheral clock cycle. In Fast Mode, clear for one system clock period and set for TPS+1

clocks per peripheral clock cycle. This bit affects the timer increment rate.

T0X2

Timer 0 Clock. In Compatibility Mode, clear for TPS+1 system clock periods per peripheral clock cycle and set for

2(TPS+1) clock periods per peripheral clock cycle. In Fast Mode, clear for one system clock period and set for TPS+1

clocks per peripheral clock cycle. This bit affects the timer increment rate.

CPU Clock. In Compatibility Mode, clear for 12 clock periods per machine cycle and set for 6 clock periods per machine

cycle. In Fast Mode, clear for two clock periods per instruction cycle and set for one clock periods per instruction cycle.

The default state of X2 is set by the X2 Fuse. See Section 24.2 on page 188.

Symbol

Function

SYSTEM CLOCK

÷2

T0X2

÷(TPS+1)

Timer 0

÷2

Timer 1

T1X2

Timer 2

T2X2

Watchdog

WDX2

PCA

(CPS = 00B)

PCAX2

PCA

(CPS = 01B)

PCAX2

SIX2 & X2

UART

SPIX2 & X2

SPI

TWIX2 & X2

TWI

SYSTEM CLOCK

T0X2

÷(TPS+1)

Timer 0

÷2

Timer 1

T1X2

Timer 2

T2X2

Watchdog

WDX2

PCA

(CPS = 00B)

PCAX2

PCA

(CPS = 01B)

PCAX2

SIX2 & X2

UART

SPIX2 & X2

SPI

TWIX2 & X2

TWI

Fast Mode

Compatibility Mode

AT89LP51RB2 Datasheet(PDF) 49 Page - ATMEL Corporation

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