LM3S9B81 Datasheet, PDF (809/1155 Pages) Texas Instruments – Stellaris® LM3S9B81 Microcontroller

Stellaris® LM3S9B81 Microcontroller
Table 19-3. TX & RX FIFO Organization
FIFO Word Read/Write
Sequence
Word Bit Fields
TX FIFO (Write)
RX FIFO (Read)
1st
7:0
Data Length Least Significant Frame Length Least
Byte
Significant Byte
15:8
Data Length Most Significant Frame Length Most Significant
Byte
Byte
23:16
DA oct 1
31:24
DA oct 2
2nd
7:0
DA oct 3
15:8
DA oct 4
23:16
DA oct 5
31:24
DA oct 6
3rd
7:0
SA oct 1
15:8
SA oct 2
23:16
SA oct 3
31:24
SA oct 4
4th
7:0
SA oct 5
15:8
SA oct 6
23:16
Len/Type Most Significant Byte
31:24
Len/Type Least Significant Byte
5th to nth
7:0
data oct n
15:8
data oct n+1
23:16
data oct n+2
31:24
last
7:0
15:8
23:16
31:24
data oct n+3
FCS 1^a
FCS 2^a
FCS 3^a
FCS 4^a
a. If the CRC bit in the MACTCTL register is clear, the FCS bytes must be written with the correct CRC. If the CRC bit is set,
the Ethernet Controller automatically writes the FCS bytes.
19.3.1.3
Ethernet Transmission Options
At the MAC layer, the transmitter can be configured for both full-duplex and half-duplex operation
by using the DUPLEX bit in the MACTCTL register. Note that in 10BASE-T half-duplex mode, the
transmitted data is looped back on the receive path.
The Ethernet Controller automatically generates and inserts the Frame Check Sequence (FCS) at
the end of the transmit frame when the CRC bit in the MACTCTL register is set. However, for test
purposes, this feature can be disabled in order to generate a frame with an invalid CRC by clearing
the CRC bit.
The IEEE 802.3 specification requires that the Ethernet frame payload section be a minimum of 46
bytes. The Ethernet Controller automatically pads the data section if the payload data section loaded
into the FIFO is less than the minimum 46 bytes when the PADEN bit in the MACTCTL register is
set. This feature can be disabled by clearing the PADEN bit.
The transmitter must be enabled by setting the TXEN bit in the MACTCTL register.
June 29, 2010
809
Texas Instruments-Advance Information