ATMEGA3250-16AUR Atmel, ATMEGA3250-16AUR Datasheet - Page 185

• Manufacturer Part Number: ATMEGA3250-16AUR
• Description: MCU AVR 32K FLASH 16MHZ 100TQFP
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA3250-16AUR

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 16MHz
• Connectivity: SPI, UART/USART, USI
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 69
• Program Memory Size: 32KB (16K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 1K x 8
• Ram Size: 2K x 8
• Voltage - Supply (vcc/vdd): 2.7 V ~ 5.5 V
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: *
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

20. USI – Universal Serial Interface
20.1
2570M–AVR–04/11
Overview
The Universal Serial Interface, or USI, provides the basic hardware resources needed for serial
communication. Combined with a minimum of control software, the USI allows significantly
higher transfer rates and uses less code space than solutions based on software only. Interrupts
are included to minimize the processor load. The main features of the USI are:
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A simplified block diagram of the USI is shown on Figure 20-1. For the actual placement of I/O
pins, refer to
CPU accessible I/O Registers, including I/O bits and I/O pins, are shown in bold. The device-
specific I/O Register and bit locations are listed in the
Figure 20-1. Universal Serial Interface, Block Diagram
The 8-bit Shift Register is directly accessible via the data bus and contains the incoming and
outgoing data. The register has no buffering so the data must be read as quickly as possible to
ensure that no data is lost. The most significant bit is connected to one of two output pins
depending of the wire mode configuration. A transparent latch is inserted between the Serial
Register Output and output pin, which delays the change of data output to the opposite clock
edge of the data input sampling. The serial input is always sampled from the Data Input (DI) pin
independent of the configuration.
The 4-bit counter can be both read and written via the data bus, and can generate an overflow
interrupt. Both the Serial Register and the counter are clocked simultaneously by the same clock
source. This allows the counter to count the number of bits received or transmitted and generate
Two-wire Synchronous Data Transfer (Master or Slave)
Three-wire Synchronous Data Transfer (Master or Slave)
Data Received Interrupt
Wake up from Idle Mode
In Two-wire Mode: Wake-up from All Sleep Modes, Including Power-down Mode
Two-wire Start Condition Detector with Interrupt Capability
“Pinout ATmega3250/6450” on page 2
USIDR
USICR
USISR
2
4-bit Counter
3
2
1
0
3
2
1
0
D Q
LE
ATmega325/3250/645/6450
[1]
TIM0 COMP
0
1
and
“Register Descriptions” on page
“Pinout ATmega325/645” on page
Two-wire Clock
Control Unit
CLOCK
HOLD
DO
DI/SDA
USCK/SCL
(Output only)
(Input/Open Drain)
(Input/Open Drain)
192.
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3.