ATmega16U4 Atmel Corporation, ATmega16U4 Datasheet - Page 242
ATmega16U4
Manufacturer Part Number
ATmega16U4
Description
Manufacturer
Atmel Corporation
Specifications of ATmega16U4
Flash (kbytes)
16 Kbytes
Pin Count
44
Max. Operating Frequency
16 MHz
Cpu
8-bit AVR
# Of Touch Channels
14
Hardware Qtouch Acquisition
No
Max I/o Pins
26
Ext Interrupts
13
Usb Transceiver
1
Usb Speed
Full Speed
Usb Interface
Device
Spi
2
Twi (i2c)
1
Uart
1
Graphic Lcd
No
Video Decoder
No
Camera Interface
No
Adc Channels
12
Adc Resolution (bits)
10
Adc Speed (ksps)
15
Analog Comparators
1
Resistive Touch Screen
No
Temp. Sensor
Yes
Crypto Engine
No
Sram (kbytes)
2.1
Eeprom (bytes)
512
Self Program Memory
YES
Dram Memory
No
Nand Interface
No
Picopower
No
Temp. Range (deg C)
-40 to 85
I/o Supply Class
2.7 to 5.5
Operating Voltage (vcc)
2.7 to 5.5
Fpu
No
Mpu / Mmu
no / no
Timers
4
Output Compare Channels
12
Input Capture Channels
2
Pwm Channels
8
32khz Rtc
No
Calibrated Rc Oscillator
Yes
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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
242
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