ATMEGA32U4-MU Atmel, ATMEGA32U4-MU Datasheet - Page 242

• Manufacturer Part Number: ATMEGA32U4-MU
• Description: MCU AVR 32K FLASH 16MHZ 44-QFN
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA32U4-MU

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 16MHz
• Connectivity: I²C, SPI, UART/USART, USB
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 26
• Program Memory Size: 32KB (16K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 1K x 8
• Ram Size: 2.5K 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
• Package: 44QFN EP
• Device Core: AVR
• Family Name: ATmega
• Maximum Speed: 16 MHz
• Operating Supply Voltage: 3.3|5 V
• Data Bus Width: 8 Bit
• Number Of Programmable I/os: 26
• Interface Type: EBI/I2S/SPI/TWI/USART/USB
• On-chip Adc: 12-chx10-bit
• Number Of Timers: 5
• For Use With: ATSTK524 - KIT STARTER ATMEGA32M1/MEGA32C1ATSTK600 - 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: ATMEGA32U4-16MU; ATMEGA32U4-16MU

7766F–AVR–11/10
Figure 20-14. Data Transfer in Master Receiver Mode
A START condition is sent by writing the following value to TWCR:
TWEN must be written to one to enable the 2-wire Serial Interface, TWSTA must be written to
one to transmit a START condition and TWINT must be set to clear the TWINT Flag. The TWI
will then test the 2-wire Serial Bus and generate a START condition as soon as the bus
becomes free. After a START condition has been transmitted, the TWINT Flag is set by hard-
ware, and the status code in TWSR will be 0x08 (See
SLA+R must be transmitted. This is done by writing SLA+R to TWDR. Thereafter the TWINT bit
should be cleared (by writing it to one) to continue the transfer. This is accomplished by writing
the following value to TWCR:
When SLA+R have been transmitted and an acknowledgement bit has been received, TWINT is
set again and a number of status codes in TWSR are possible. Possible status codes in Master
mode are 0x38, 0x40, or 0x48. The appropriate action to be taken for each of these status codes
is detailed in
Flag is set high by hardware. This scheme is repeated until the last byte has been received.
After the last byte has been received, the MR should inform the ST by sending a NACK after the
last received data byte. The transfer is ended by generating a STOP condition or a repeated
START condition. A STOP condition is generated by writing the following value to TWCR:
A REPEATED START condition is generated by writing the following value to TWCR:
After a repeated START condition (state 0x10) the 2-wire Serial Interface can access the same
Slave again, or a new Slave without transmitting a STOP condition. Repeated START enables
TWCR
value
TWCR
value
TWCR
value
TWCR
value
SDA
SCL
TWINT
TWINT
TWINT
TWINT
Table
1
1
1
1
20-4. Received data can be read from the TWDR Register when the TWINT
Device 1
RECEIVER
MASTER
TWEA
TWEA
TWEA
TWEA
X
X
X
X
TRANSMITTER
TWSTA
TWSTA
TWSTA
TWSTA
Device 2
SLAVE
1
0
0
1
TWSTO
TWSTO
TWSTO
TWSTO
Device 3
0
0
1
0
........
TWWC
TWWC
TWWC
TWWC
X
X
X
X
Table
Device n
TWEN
TWEN
TWEN
TWEN
20-3). In order to enter MR mode,
V
1
1
1
1
CC
ATmega16/32U4
R1
–
0
–
0
–
0
–
0
R2
TWIE
TWIE
TWIE
TWIE
X
X
X
X
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