AT91SAM7A1-AU Atmel, AT91SAM7A1-AU Datasheet - Page 279

• Manufacturer Part Number: AT91SAM7A1-AU
• Description: IC ARM7 MCU 32BIT ROMLESS144LQFP
• Manufacturer: Atmel
• Series: AT91SAMr

Specifications of AT91SAM7A1-AU

• Core Processor: ARM7
• Core Size: 16/32-Bit
• Speed: 40MHz
• Connectivity: CAN, EBI/EMI, SPI, UART/USART
• Peripherals: POR, PWM, WDT
• Number Of I /o: 49
• Program Memory Type: ROMless
• Ram Size: 4K x 8
• Voltage - Supply (vcc/vdd): 3 V ~ 3.6 V
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 144-LQFP
• For Use With: AT91SAM7A1-EK - BOARD EVAL FOR AT91SAM7A1
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Eeprom Size: -
• Program Memory Size: -

25.4.3.2
Figure 25-9. Remote Frame
6048B–ATARM–29-Jun-06
Interframe
Space
Remote Frame
SOF
Figure 25-8. ACK Field
All nodes having received the matching CRC sequence report this within the ACK slot by over-
writing the recessive bit of the transmitter by a dominant bit.
The ACK delimiter is the second bit of the ACK field and has to be a recessive bit. As a conse-
quence, the ACK slot is surrounded by two recessive bits (CRC delimiter, ACK delimiter).
End Of Frame (Standard and Extended Format)
Each data frame and remote frame is delimited by seven recessive bits. These bits form the
end of frame sequence (EOF).
A node acting as a receiver for certain data can initiate the transmission of the respective data
by its source node by sending a remote frame. A remote frame exists both in standard format
and in extended format. In both cases, it is composed of six different bit fields:
Contrary to data frames, the RTR bit of remote frames is recessive. There is no data field,
independent of the values of the data length code which may be signed any value within the
admissible range from 0 to 8. The value is the data length code of the corresponding data
frame.
The polarity of the RTR bit (CAN_IRX register) indicates whether a transmitted frame is a data
frame (RTR bit dominant) or a remote frame (RTR bit recessive).
If a mailbox is set to reply automatically to the remote frame (RPLYV bit set to logical 1 in
CAN_CRx register), the CAN module automatically sends a message with the identifier and
data contained in that mailbox after receiving the remote frame.
• ACK Slot
• ACK Delimiter
• Start Of Frame (SOF)
• Arbitration field
• Control field
• CRC field
• ACK field
• End Of Frame
Arbitration
Field
CRC Field
Control
Field
Remote Frame
ACK Slot
ACK Field
CRC
Field
ACK Delimiter
ACK
Field
EOF
EOF
AT91SAM7A1
Interframe Space
or Overload Frame
279