ATmega406 Atmel Corporation, ATmega406 Datasheet - Page 168

• Manufacturer Part Number: ATmega406
• Manufacturer: Atmel Corporation

Specifications of ATmega406

• Flash (kbytes): 40 Kbytes
• Pin Count: 48
• Max. Operating Frequency: 1 MHz
• Cpu: 8-bit AVR
• # Of Touch Channels: 8
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 18
• Ext Interrupts: 4
• Usb Speed: No
• Usb Interface: No
• Twi (i2c): 1
• Graphic Lcd: No
• Video Decoder: No
• Camera Interface: No
• Adc Channels: 11
• Adc Resolution (bits): 12
• Adc Speed (ksps): 1.9
• Resistive Touch Screen: No
• Temp. Sensor: Yes
• Crypto Engine: No
• Sram (kbytes): 2
• Eeprom (bytes): 512
• Self Program Memory: YES
• Dram Memory: No
• Nand Interface: No
• Picopower: No
• Temp. Range (deg C): -30 to 85
• I/o Supply Class: 4.0 to 25
• Operating Voltage (vcc): 4.0 to 25
• Fpu: No
• Mpu / Mmu: no / no
• Timers: 2
• Output Compare Channels: 3
• Pwm Channels: 2
• 32khz Rtc: Yes
• Calibrated Rc Oscillator: Yes

168
ATmega406
Figure 25-21. An Arbitration Example
Several different scenarios may arise during arbitration, as described below:
• Two or more masters are performing identical communication with the same slave. In this case,
• Two or more masters are accessing the same slave with different data or direction bit. In this
• Two or more masters are accessing different slaves. In this case, arbitration will occur in the
This is summarized in
Figure 25-22. Possible Status Codes Caused by Arbitration
neither the slave nor any of the masters will know about the bus contention.
case, arbitration will occur, either in the READ/WRITE bit or in the data bits. The masters trying
to output a one on SDA while another master outputs a zero will lose the arbitration. Losing
masters will switch to not addressed Slave mode or wait until the bus is free and transmit a new
START condition, depending on application software action.
SLA bits. Masters trying to output a one on SDA while another master outputs a zero will lose
the arbitration. Masters losing arbitration in SLA will switch to Slave mode to check if they are
being addressed by the winning master. If addressed, they will switch to SR or ST mode,
depending on the value of the READ/WRITE bit. If they are not being addressed, they will
switch to not addressed Slave mode or wait until the bus is free and transmit a new START
condition, depending on application software action.
SDA
SCL
START
TRANSMITTER
Device 1
MASTER
Address / General Call
Figure
Direction
received
Own
TRANSMITTER
Yes
Device 2
Arbitration lost in SLA
MASTER
SLA
25-22. Possible status values are given in circles.
Write
Read
No
Device 3
RECEIVER
SLAVE
68/78
38
B0
........
Arbitration lost in Data
TWI bus will be released and not addressed slave mode will be entered
A START condition will be transmitted when the bus becomes free
Data byte will be received and NOT ACK will be returned
Data byte will be received and ACK will be returned
Last data byte will be transmitted and NOT ACK should be received
Data byte will be transmitted and ACK should be received
Device n
V
Data
BUS
R1
R2
2548E–AVR–07/06
STOP