AT91RM9200-CI-002 Atmel, AT91RM9200-CI-002 Datasheet - Page 607

• Manufacturer Part Number: AT91RM9200-CI-002
• Description: IC ARM9 MCU 256 BGA
• Manufacturer: Atmel
• Series: AT91SAMr

Specifications of AT91RM9200-CI-002

• Core Processor: ARM9
• Core Size: 16/32-Bit
• Speed: 180MHz
• Connectivity: EBI/EMI, Ethernet, I²C, MMC, SPI, SSC, UART/USART, USB
• Peripherals: POR
• Number Of I /o: 122
• Program Memory Size: 128KB (128K x 8)
• Program Memory Type: ROM
• Ram Size: 48K x 8
• Voltage - Supply (vcc/vdd): 1.65 V ~ 1.95 V
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 256-BGA
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Eeprom Size: -
• Data Converters: -

36.5.4
1768I–ATARM–09-Jul-09
DMA Operations
allowable frame size to 1522 bytes to allow a VLAN tag to be inserted into the Ethernet frame
format. The bit BIG defined in the ETH_CFG register aims to process packet with VLAN tag.
The VLAN protocol permits insertion of an identifier, or tag, into the Ethernet frame format to
identify the VLAN to which the frame belongs. It allows frames from stations to be assigned to
logical groups. This provides various benefits, such as easing network administration, allowing
formation of work groups, enhancing network security, and providing a means of limiting broad-
cast domains (refer to IEEE standard 802.1Q for definition of the VLAN protocol). The 802.3ac
standard defines only the implementation details of the VLAN protocol that are specific to
Ethernet.
If present, the 4-byte VLAN tag is inserted into the Ethernet frame between the Source MAC
Address field and the Length field. The first 2-bytes of the VLAN tag consist of the “802.1Q Tag
Type” and are always set to a value of 0x8100. The 0x8100 value is a reserved Length/Type
field assignment that indicates the presence of the VLAN tag, and signals that the traditional
Length/Type field can be found at an offset of four bytes further into the frame. The last two
bytes of the VLAN tag contain the following information:
With the addition of VLAN tagging, the 802.3ac standard permits the maximum length of an
Ethernet frame to be extended from 1518 bytes to 1522 bytes.
of an Ethernet frame that has been “tagged” with a VLAN identifier according to the IEEE
802.3ac standard.
Table 36-3.
Frame data is transferred to and from the Ethernet MAC via the DMA interface. All transfers are
32-bit words and may be single accesses or bursts of two, three or four words. Burst accesses
do not cross 16-byte boundaries.
Preamble
Start Frame Delimiter
Dest. MAC Address
Source MAC Address
Length/Type = 802.1Q Tag Type
Tag Control Information
Length / Type
MAC Client Data
Pad
Frame Check Sequence
• The first three bits are a User Priority Field that may be used to assign a priority level to the
• The following one bit is a Canonical Format Indicator (CFI) used in Ethernet frames to
• The last twelve bits are the VLAN Identifier (VID) that uniquely identifies the VLAN to which
Ethernet frame.
indicate the presence of a Routing Information Field (RIF).
the Ethernet frame belongs.
Ethernet Frame with VLAN Tagging
Table 36-3
AT91RM9200
0 - n bytes
0 - p bytes
illustrates the format
7 bytes
6 bytes
2 bytes
4 bytes
6 bytes
2 bytes
1 byte
2 byte
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