ATmega16M1 Automotive Atmel Corporation, ATmega16M1 Automotive Datasheet - Page 169

• Manufacturer Part Number: ATmega16M1 Automotive
• Manufacturer: Atmel Corporation

Specifications of ATmega16M1 Automotive

• Flash (kbytes): 16 Kbytes
• Pin Count: 32
• Max. Operating Frequency: 16 MHz
• Cpu: 8-bit AVR
• # Of Touch Channels: 12
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 27
• Ext Interrupts: 27
• Usb Speed: No
• Usb Interface: No
• Spi: 1
• Uart: 1
• Can: 1
• Lin: 1
• Graphic Lcd: No
• Video Decoder: No
• Camera Interface: No
• Adc Channels: 11
• Adc Resolution (bits): 10
• Adc Speed (ksps): 125
• Analog Comparators: 4
• Resistive Touch Screen: No
• Dac Channels: 1
• Dac Resolution (bits): 10
• Temp. Sensor: Yes
• Crypto Engine: No
• Sram (kbytes): 1
• Eeprom (bytes): 512
• Self Program Memory: YES
• Dram Memory: No
• Nand Interface: No
• Picopower: No
• Temp. Range (deg C): -40 to 150
• I/o Supply Class: 2.7 to 5.5
• Operating Voltage (vcc): 2.7 to 5.5
• Fpu: No
• Mpu / Mmu: no / no
• Timers: 2
• Output Compare Channels: 14
• Input Capture Channels: 1
• Pwm Channels: 10
• 32khz Rtc: No
• Calibrated Rc Oscillator: Yes

16.2.2
16.2.2.1
Figure 16-1. CAN Standard Frames
7647G–AVR–09/11
Message Formats
Can Standard Frame
Interframe
Interframe
Data Frame
Remote Frame
Space
Space
Bus Idle
Bus Idle
SOF
SOF
SOF
SOF
Bus access conflicts are resolved by bit-wise arbitration on the identifiers involved by each
node observing the bus level bit for bit. This happens in accordance with the "wired and"
mechanism, by which the dominant state overwrites the recessive state. The competition for
bus allocation is lost by all nodes with recessive transmission and dominant observation. All
the "losers" automatically become receivers of the message with the highest priority and do
not re-attempt transmission until the bus is available again.
The CAN protocol supports two message frame formats, the only essential difference being in
the length of the identifier. The CAN standard frame, also known as CAN 2.0 A, supports a
length of 11 bits for the identifier, and the CAN extended frame, also known as CAN 2.0 B,
supports a length of 29 bits for the identifier.
A message in the CAN standard frame format begins with the "Start Of Frame (SOF)", this is
followed by the "Arbitration field" which consist of the identifier and the "Remote Transmission
Request (RTR)" bit used to distinguish between the data frame and the data request frame
called remote frame. The following "Control field" contains the "IDentifier Extension (IDE)" bit
and the "Data Length Code (DLC)" used to indicate the number of following data bytes in the
"Data field". In a remote frame, the DLC contains the number of requested data bytes. The
"Data field" that follows can hold up to 8 data bytes. The frame integrity is guaranteed by the
following "Cyclic Redundant Check (CRC)" sum. The "ACKnowledge (ACK) field" compro-
mises the ACK slot and the ACK delimiter. The bit in the ACK slot is sent as a recessive bit
and is overwritten as a dominant bit by the receivers which have at this time received the data
correctly. Correct messages are acknowledged by the receivers regardless of the result of the
acceptance test. The end of the message is indicated by "End Of Frame (EOF)". The "Inter-
mission Frame Space (IFS)" is the minimum number of bits separating consecutive
messages. If there is no following bus access by any node, the bus remains idle.
11-bit identifier
11-bit identifier
ID10..0
ID10..0
Arbitration
Arbitration
Field
Field
RTR IDE r0
RTR IDE r0
Control
Control
Field
Field
4-bit DLC
4-bit DLC
DLC4..0
DLC4..0
15-bit CRC
CRC
Field
Atmel ATmega16/32/64/M1/C1
0 - 8 bytes
Data
Field
CRC
del.
ACK
ACK
Field
ACK
del.
End of
Frame
7 bits
15-bit CRC
CRC
Field
Intermission
3 bits
CRC
del.
Interframe
ACK
Space
Field
ACK
(Indefinite)
ACK
Bus Idle
del.
End of
Frame
7 bits
Intermission
3 bits
Interframe
Space
(Indefinite)
Bus Idle
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