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60 Intel 8255x 10/100 Mbps Ethernet Controller Family Open Source Software Developer Manual
Host Software Interface
After reading the command and determining it is a NOP, the device CU performs the following
sequence:
1. Begins execution of the NOP action command.
2. Prepares the status word with C equal to 1 and OK equal to 1.
3. Completes the NOP action command.
6.4.2.2 Individual Address Setup (001b)
This command is used to load the device with the individual address. This address is used by the
device for inserting the source address during transmission and recognizing the destination address
during reception. After a full reset and prior to individual address setup command execution, the
device assumes the broadcast address (FF FF FF FF FF FFh) is the individual address in all
respects.
This address loaded into the device is used as the individual address match reference. It will also be
used as the source address of a transmitted frame (if the no source address insertion bit equals 0).
CMD (Bits 18:16) This is the NOP command, which has a value of 000b.
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).
Figure 16. Individual Address Setup Command Format
Offset Command Word Bits 31:16 Status Word Bits 15:0
00h EL S I 0000000000 001 C X OK XXXXXXXXXXXXX
04h Link Address (A31:A0)
08h IA 4th Byte, IA 3rd Byte IA 2nd Byte, IA 1st Byte
0Ch IA 6th Byte, IA 5th Byte
Link Address
This is the 32-bit address of the next command block. It is added to the CU base to
obtain the actual address.
EL (Bit 31)
If this bit is set to one, it indicates that this command block is the last one on the CBL.
The CU will go from the active to the idle state after the execution of the CB is finished.
This transition will always cause an interrupt with the CNA/CI bit set in the SCB.
S (Bit 30)
If this bit is set to one, the CU will be suspended after the completion of this CB. A CNA
interrupt will be generated if the device is configured for this. The CU transitions from the
active to the suspended state after the execution of the CB.
I (Bit 29)
If the I bit is set to one, the device generates an interrupt after the execution of the CB is
finished. If I is not set to one, the CX interrupt will not be generated.
Bits 28:19 These bits are reserved and should all be set to 0.