AT91RM9200-QI-002 Atmel, AT91RM9200-QI-002 Datasheet - Page 606

• Manufacturer Part Number: AT91RM9200-QI-002
• Description: IC ARM9 MCU 208 PQFP
• Manufacturer: Atmel
• Series: AT91SAMr

Specifications of AT91RM9200-QI-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: 208-MQFP, 208-PQFP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Eeprom Size: -
• Data Converters: -

36.5.2.1
36.5.2.2
36.5.2.3
36.5.2.4
36.5.2.5
36.5.2.6
36.5.3
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AT91RM9200
Frame Format Extensions
Preamble and Start of Frame Delimiter (SFD)
Destination Address
Source Address
Length/Type
LLC Data
FCS Field
Note:
The packets are Manchester-encoded and -decoded and transferred serially using NRZ data
with a clock. All fields are of fixed length except for the data field. The MAC generates and
appends the preamble, SFD and CRC fields during transmission.
The preamble and SFD fields are stripped during reception.
The preamble field is used to acquire bit synchronization with an incoming packet. When trans-
mitted, each packet contains 62 bits of alternating 1,0 preamble. Some of this preamble is lost
as the packet travels through the network. Byte alignment is performed with the Start of Frame
Delimiter (SFD) pattern that consists of two consecutive 1's.
The destination address (DA) indicates the destination of the packet on the network and is used
to filter unwanted packets. There are three types of address formats: physical, multicast and
broadcast. The physical address is a unique address that corresponds only to a single node. All
physical addresses have an MSB of 0.
Multicast addresses begin with an MSB of 1. The MAC filters multicast addresses using a stan-
dard hashing algorithm that maps all multicast addresses into a 6-bit value. This 6-bit value
indexes a 64-bit array that filters the value. If the address consists of all ones, it is a broadcast
address, indicating that the packet is intended for all nodes.
The source address (SA) is the physical address of the node that sent the packet. Source
addresses cannot be multicast or broadcast addresses. This field is passed to buffer memory.
If the value of this field is less than or equal to 1500, then the Length/Type field indicates the
number of bytes in the subsequent LLC Data field. If the value of this field is greater than or
equal to 1536, then the Length/Type field indicates the nature of the MAC client protocol (proto-
col type).
The data field consists of anywhere from 46 to 1500 bytes. Messages longer than 1500 bytes
need to be broken into multiple packets. Messages shorter than 46 bytes require appending a
pad to bring the data field to the minimum length of 46 bytes. If the data field is padded, the num-
ber of valid data bytes is indicated in the length field.
The Frame Check Sequence (FCS) is a 32-bit CRC field, calculated and appended to a packet
during transmission to allow detection of errors when a packet is received. During reception,
error free packets result in a specific pattern in the CRC generator. Packets with improper CRC
will be rejected.
The original Ethernet standards defined the minimum frame size as 64 bytes and the maximum
as 1518 bytes. These numbers include all bytes from the Destination MAC Address field through
the Frame Check Sequence field. The Preamble and Start Frame Delimiter fields are not
included when quoting the size of a frame. The IEEE 802.3ac standard extended the maximum
Frame Length between 64 bytes and 1518 bytes.
1768I–ATARM–09-Jul-09