ATMEGA16U4-MU Atmel, ATMEGA16U4-MU Datasheet - Page 40

• Manufacturer Part Number: ATMEGA16U4-MU
• Description: MCU AVR 16K FLASH 16MHZ 44-QFN
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA16U4-MU

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 16MHz
• Connectivity: I²C, SPI, UART/USART, USB
• Peripherals: Brown-out Detect/Reset, POR, PWM, Temp Sensor, WDT
• Number Of I /o: 26
• Program Memory Size: 16KB (8K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 512 x 8
• Ram Size: 1.25K x 8
• Voltage - Supply (vcc/vdd): 2.7 V ~ 5.5 V
• Data Converters: A/D 12x10b
• Oscillator Type: External
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 44-VQFN
• For Use With: ATSTK600 - DEV KIT FOR AVR/AVR32ATAVRDRAGON - KIT DRAGON 32KB FLASH MEM AVRATSTK500 - PROGRAMMER AVR STARTER KIT
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: ATMEGA16U4-16MU; ATMEGA16U4-16MU

6.10.2
6.10.3
7766F–AVR–11/10
PLL Control and Status Register – PLLCSR
PLL Frequency Control Register – PLLFRQ
Figure 6-6.
• Bit 7..5 – Res: Reserved Bits
These bits are reserved bits in the ATmega16U4/ATmega32U4 and always read as zero.
• Bit 4 – PINDIV PLL Input Prescaler (1:1, 1:2)
These bits allow to configure the PLL input prescaler to generate the 8MHz input clock for the
PLL from either a 8 or 16 MHz input.
When using a 8 MHz clock source, this bit must be set to 0 before enabling PLL (1:1).
When using a 16 MHz clock source, this bit must be set to 1 before enabling PLL (1:2).
• Bit 3..2 – Res: Reserved Bits
These bits are reserved bits in the ATmega16U4/ATmega32U4 and always read as zero.
• Bit 1 – PLLE: PLL Enable
When the PLLE is set, the PLL is started. Note that the Calibrated 8 MHz Internal RC oscillator is
automatically enabled when the PLLE bit is set and with PINMUX (see PLLFRQ register) is set.
The PLL must be disabled before entering Power down mode in order to stop Internal RC Oscil-
lator and avoid extra-consumption.
• Bit 0 – PLOCK: PLL Lock Detector
When the PLOCK bit is set, the PLL is locked to the reference clock. After the PLL is enabled, it
takes about several ms for the PLL to lock. To clear PLOCK, clear PLLE.
XTAL1
XTAL2
Bit
$29 ($29)
Read/Write
Initial Value
Bit
$32
Read/Write
Initial Value
RC OSCILLATOR
8 MHz
OSCILLATOR
XTAL
7
R
0
7
PINMUX
R/W
0
PLL Clocking System
6
R
0
6
PLLUSB
R/W
0
CKSEL3:0
5
R
0
5
PLLTM1
R/W
0
To System
Clock Prescaler
PLL clock
Prescaler
PINDIV
4
PINDIV
R/W
0
4
PLLTM0
R/W
0
3
R
0
3
R/W
0
PINMUX
PDIV3
0
1
clk
8MHz
2
R
0
2
R/W
1
PLOCK
PDIV2
Detector
Lock
PDIV3..0
PLL
ATmega16/32U4
PLLE
1
PLLE
R/W
0
1
R/W
0
PDIV1
/1.5
0
PLOCK
R
0
0
R/W
0
/2
PDIV0
PLLTM1:0
PLLUSB
10
11
01
1
0
PLLCSR
PLLFRQ
clk TMR
clk USB
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