AT32UC3A1512 Atmel Corporation, AT32UC3A1512 Datasheet - Page 442

• Manufacturer Part Number: AT32UC3A1512
• Manufacturer: Atmel Corporation

Specifications of AT32UC3A1512

• Flash (kbytes): 512 Kbytes
• Pin Count: 100
• Max. Operating Frequency: 66 MHz
• Cpu: 32-bit AVR
• # Of Touch Channels: 32
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 69
• Ext Interrupts: 69
• Usb Transceiver: 1
• Usb Speed: Full Speed
• Usb Interface: Device + OTG
• Spi: 6
• Twi (i2c): 1
• Uart: 4
• Ssc: 1
• Ethernet: 1
• Graphic Lcd: No
• Video Decoder: No
• Camera Interface: No
• Adc Channels: 8
• Adc Resolution (bits): 10
• Adc Speed (ksps): 384
• Resistive Touch Screen: No
• Dac Channels: 2
• Dac Resolution (bits): 16
• Temp. Sensor: No
• Crypto Engine: No
• Sram (kbytes): 64
• Self Program Memory: YES
• Dram Memory: No
• Nand Interface: No
• Picopower: No
• Temp. Range (deg C): -40 to 85
• I/o Supply Class: 3.0-3.6 or (1.65-1.95+3.0-3.6)
• Operating Voltage (vcc): 3.0-3.6 or (1.65-1.95+3.0-3.6)
• Fpu: No
• Mpu / Mmu: Yes / No
• Timers: 10
• Output Compare Channels: 16
• Input Capture Channels: 6
• Pwm Channels: 13
• 32khz Rtc: Yes
• Calibrated Rc Oscillator: Yes

AT32UC3A
For CRC errored frames, excessive length frames or length field mismatched frames, all of
which are counted in the statistics registers, it is possible that a frame fragment might be stored
in a sequence of receive buffers. Software can detect this by looking for start of frame bit set in a
buffer following a buffer with no end of frame bit set.
For a properly working Ethernet system, there should be no excessively long frames or frames
greater than 128 bytes with CRC/FCS errors. Collision fragments are less than 128 bytes long.
Therefore, it is a rare occurrence to find a frame fragment in a receive buffer.
If bit zero is set when the receive buffer manager reads the location of the receive buffer, then
the buffer has already been used and cannot be used again until software has processed the
frame and cleared bit zero. In this case, the DMA block sets the buffer not available bit in the
receive status register and triggers an interrupt.
If bit zero is set when the receive buffer manager reads the location of the receive buffer and a
frame is being received, the frame is discarded and the receive resource error statistics register
is incremented.
A receive overrun condition occurs when bus was not granted in time or because HRESP was
not OK (bus error). In a receive overrun condition, the receive overrun interrupt is asserted and
the buffer currently being written is recovered. The next frame received with an address that is
recognized reuses the buffer.
If bit 17 of the network configuration register is set, the FCS of received frames shall not be cop-
ied to memory. The frame length indicated in the receive status field shall be reduced by four
bytes in this case.
29.5.1.3
Transmit Buffer
Frames to be transmitted are stored in one or more transmit buffers. Transmit buffers can be
between 0 and 2047 bytes long, so it is possible to transmit frames longer than the maximum
length specified in IEEE Standard 802.3. Zero length buffers are allowed. The maximum number
of buffers permitted for each transmit frame is 128.
The start location for each transmit buffer is stored in memory in a list of transmit buffer descrip-
tors at a location pointed to by the transmit buffer queue pointer register. Each list entry consists
of two words, the first being the byte address of the transmit buffer and the second containing
the transmit control and status. Frames can be transmitted with or without automatic CRC gen-
eration. If CRC is automatically generated, padding is also automatically generated to take
frames to a minimum length of 64 bytes.
Table 29-2 on page 443
defines an entry in the transmit
buffer descriptor list. To transmit frames, the buffer descriptors must be initialized by writing an
appropriate byte address to bits 31 to 0 in the first word of each list entry. The second transmit
buffer descriptor is initialized with control information that indicates the length of the buffer,
whether or not it is to be transmitted with CRC and whether the buffer is the last buffer in the
frame.
After transmission, the control bits are written back to the second word of the first buffer along
with the “used” bit and other status information. Before a transmission, bit 31 is the “used” bit
which must be zero when the control word is read. It is written to one when a frame has been
transmitted. Bits 27, 28 and 29 indicate various transmit error conditions. Bit 30 is the “wrap” bit
which can be set for any buffer within a frame. If no wrap bit is encountered after 1024 descrip-
tors, the queue pointer rolls over to the start.
The transmit buffer queue pointer register must not be written while transmit is active. If a new
value is written to the transmit buffer queue pointer register, the queue pointer resets itself to
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32058K AVR32-01/12