ATEVK1105 Atmel, ATEVK1105 Datasheet - Page 444

• Manufacturer Part Number: ATEVK1105
• Description: KIT EVAL FOR AT32UC3A0
• Manufacturer: Atmel
• Series: AVR®32r
• Type: MCUr

Specifications of ATEVK1105

• Contents: Evaluation Board, Software and Documentation
• Processor To Be Evaluated: AT32UC3A0512
• Processor Series: AVR
• Data Bus Width: 32 bit
• Interface Type: USART, TWI, USB, SPI, Ethernet
• Operating Supply Voltage: 3.3 V
• Silicon Manufacturer: Atmel
• Core Architecture: AVR
• Core Sub-architecture: AVR UC3
• Silicon Core Number: AT32UC3A0512
• Silicon Family Name: AVR
• Kit Contents: Board CD Docs
• Rohs Compliant: Yes
• For Use With/related Products: AT32UC3A0
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Table 29-2.
29.5.2
29.5.3
32058J–AVR32–04/11
Bit
14:11
10:0
16
15
Transmit Block
Pause Frame Support
No CRC. When set, no CRC is appended to the current frame. This bit only needs to be set for the last buffer of a frame.
Last buffer. When set, this bit indicates the last buffer in the current frame has been reached.
Reserved
Length of buffer
Transmit Buffer Descriptor Entry (Continued)
This block transmits frames in accordance with the Ethernet IEEE 802.3 CSMA/CD protocol.
Frame assembly starts by adding preamble and the start frame delimiter. Data is taken from the
transmit FIFO a word at a time. Data is transmitted least significant nibble first. If necessary,
padding is added to increase the frame length to 60 bytes. CRC is calculated as a 32-bit polyno-
mial. This is inverted and appended to the end of the frame, taking the frame length to a
minimum of 64 bytes. If the No CRC bit is set in the second word of the last buffer descriptor of a
transmit frame, neither pad nor CRC are appended.
In full-duplex mode, frames are transmitted immediately. Back-to-back frames are transmitted at
least 96 bit times apart to guarantee the interframe gap.
In half-duplex mode, the transmitter checks carrier sense. If asserted, it waits for it to de-assert
and then starts transmission after the interframe gap of 96 bit times. If the collision signal is
asserted during transmission, the transmitter transmits a jam sequence of 32 bits taken from the
data register and retries transmission after the back off time has elapsed.
The back-off time is based on an XOR of the 10 least significant bits of the data coming from the
transmit FIFO and a 10-bit pseudo random number. The number of bits used depends on the
number of collisions seen. After the first collision, 1 bit is used, after the second 2, and so on up
to 10. Above 10, all 10 bits are used. An error is indicated and no further attempts are made if 16
attempts cause collisions.
If transmit DMA underruns, bad CRC is automatically appended using the same mechanism as
jam insertion and the TX_ER signal is asserted. In a properly configured system, this should
never happen.
If the back pressure bit is set in the network control register in half duplex mode, the transmit
block transmits 64 bits of data, which can consist of 16 nibbles of 1011 or in bit-rate mode 64 1s,
whenever it sees an incoming frame to force a collision. This provides a way of implementing
flow control in half-duplex mode.
The start of an 802.3 pause frame is as follows:
Table 29-3.
The network configuration register contains a receive pause enable bit (13). If a valid pause
frame is received, the pause time register is updated with the frame’s pause time, regardless of
Destination Address
0x0180C2000001
Start of an 802.3 Pause Frame
Address
Source
6 bytes
Function
(Mac Control Frame)
0x8808
Type
Opcode
0x0001
Pause
AT32UC3A
Pause Time
2 bytes
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