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Intel 8255x 10/100 Mbps Ethernet Controller Family Open Source Software Developer Manual 61
Host Software Interface
The individual address is transferred by the transmit DMA through the transmit FIFO to the
execution machine in the CSMA/CD module. Therefore, it may take some time to execute. The
execution unit maintains a 48-bit individual address register used for source address insertion
during transmission and for destination address recognition during reception. A reset causes the
individual address register to be set to FF FF FF FF FF FFh.
After reading the command and determining whether it is an IA setup command, the device CU
performs the following sequence:
1. Begins execution of the IA setup action command.
2. Initiates the transmit DMA with the address of the first byte of the individual address and a
byte count of 6.
3. Waits for the transmit byte machine to complete the internal update of the individual address
register.
4. Completes the IA setup action command.
6.4.2.3 Configure (010b)
The configure command loads the device with its operating parameters. A maximum of 22
configuration bytes are supported. The first eight bytes are used by the CU, and the remaining
bytes are passed to the CSMA/CD unit through the transmit DMA. The minimum number of
configuration bytes is 8.
Parameters not configured automatically use default values. The only exception is the PHY
interface configuration bit. For 82557 based adapters, this bit must be set to either a zero or one
before the 82557 will transmit or receive frames. For 82558 and later generation controllers, this
bit must be set to 1 before the device will send and receive.
CMD (Bits 18:16) This is the Individual Address Setup command, which has a value of 001b.
C (Bit 15)
This bit indicates the execution status of the command. Software should reset this bit
before issuing the command to the device. Following a command completion, the device
sets it to one.
NOTE: The difference in the definition of the C bit for the transmit command
(Section 6.4.2.5).
OK (Bit 13)
The OK bit indicates that the command was executed without error. If it equals one, no
error occurred (command executed OK). If the OK bit is zero and the C bit is set, then an
error occurred.
NOTE: The difference in the definition of the C bit for the transmit command
(Section 6.4.2.5).
Individual
Address
The individual address of the node is 6 bytes long. IA byte 1 corresponds to the first byte
of the address that is transmitted over the wire. For example, if the node address is 00
AA 00 01 02 03h, the bytes will be programmed as follows:
IA Byte 1 00h
IA Byte 2 AAh
IA Byte 3 00h
IA Byte 4 01h
IA Byte 5 02h
IA Byte 6 03h