AT90PWM2B-16SU View Datasheet(PDF) - Atmel Corporation

Part Name

Description

Manufacturer

AT90PWM2B-16SU

8-bit Atmel Microcontroller with 8K Bytes In-System Programmable Flash

Atmel Corporation 

AT90PWM2/3/2B/3B

7.1.5

ADC Clock – clkADC

The ADC is provided with a dedicated clock domain. This allows halting the CPU and I/O clocks

in order to reduce noise generated by digital circuitry. This gives more accurate ADC conversion

results.

7.2 Clock Sources

The device has the following clock source options, selectable by Flash Fuse bits as illustrated

Table 7-1. The clock from the selected source is input to the AVR clock generator, and routed to

the appropriate modules.

Table 7-1. Device Clocking Options Select(1) AT90PWM2/3

Device Clocking Option

External Crystal/Ceramic Resonator

Reserved

PLL output divided by 4 : 16 MHz

Calibrated Internal RC Oscillator

Reserved

External Clock

Note: 1. For all fuses “1” means unprogrammed while “0” means programmed.

CKSEL3..0

1111 - 1000

0111- 0100

0011

0010

0001

0000

Table 7-2. Device Clocking Options Select AT90PWM2B/3B

Device Clocking Option

External Crystal/Ceramic Resonator

System

Clock

Ext Osc (2)

PLL Input

RC Osc (3)

PLL output divided by 4 : 16 MHz / External

Crystal/Ceramic Resonator/ PLL driven by External Crystal

/Ceramic Resonator

Ext Osc

Ext Osc

PLL output divided by 4 : 16 MHz / PLL driven by External

Crystal/Ceramic Resonator

PLL / 4

Ext Osc

Reserved

N/A

N/A

PLL output divided by 4 : 16 MHz

PLL / 4

RC Osc

Calibrated Internal RC Oscillator

RC Osc RC Osc

PLL output divided by 4 : 16 MHz / PLL driven by External

clock

PLL / 4

Ext Clk (4)

External Clock

Ext Clk

RC Osc

1.For all fuses “1” means unprogrammed while “0” means programmed

2.Ext Osc : External Osc

3.RC Osc : Internal RC Oscillator

4.Ext Clk : External Clock Input

CKSEL3..0

(1)

1111 - 1000

0100

0101

0111- 0110

0011

0010

0001

0000

4317K–AVR–03/2013

The various choices for each clocking option is given in the following sections. When the CPU

wakes up from Power-down or Power-save, the selected clock source is used to time the start-

31

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