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72 Intel 8255x 10/100 Mbps Ethernet Controller Family Open Source Software Developer Manual
Host Software Interface
Default - 0.
Recommended - 0.
— Bit 0 - Late SCB = Late SCB Update. This bit is reserved on the 82558 and 82559 and
should be set to 0 on those devices.
This bit only has meaning on the 82557 and determines when the device updates the SCB
in relation to the completion of an action command. When it equals zero, the device
updates the SCB status if there is an interrupt to report after completing the action
command and before the next action command is started. If it is set to one, the device
delays the updating of the SCB until after the next command on the CBL is started.
0 = Inactive (update SCB after command completion).
1 = Active (update SCB after next command is started).
Default - 0.
Recommended - 0.
• BYTE 7.
— Bit 6 - Two Frames in FIFO. This bit is reserved on the 82557 and should be set to 0. It is
a valid bit for the 82558 and 82559 devices.
When this bit is set on the 82558 or 82559, the device limits the number of transmit
frames in its FIFO to no more than two. This bit is expected to be used only when the
device is used in multimedia mode.
0 = Two frames in FIFO disabled.
1 = Two frames in FIFO enabled.
Default - 0 (disabled).
Recommended - 0.
Bit 7 - Dynamic TBD. This bit is reserved on the 82557 and should be set to 0. However,
when this bit is set on the 82558 or 82559, the device checks the validity of the transmit
buffer pointer in the TBD and the EL bit in the TBD. When it is clear (0), the device
assumes that the transmit buffer pointer in the TBD is always valid and the last TBD is
indicated by the TBD count field in the transmit CB. When this configuration bit is set,
the driver should set the TBD count field in the transmit CB to FFh.
0 = Dynamic TBD disabled.
1 = Dynamic TBD enabled.
Default - 0 (disabled).
Recommended - 0 (unless reducing transmit latency is large concern).
— Bits 2:1 - Underrun Retry. This field specifies the number of transmission retries after an
underrun has occurred.
Table 45. Extended Statistics Functionality
TCO Statistical
Counters
Extended Statistical
Counters
Statistics Counters Functionality
0 1 82557 compatible (16 counters / 16 Dwords)
0 0 82558 compatible (19 counters / 19 Dwords)
1 1 82559 mode (21 counters / 24 Dwords)
10Reserved