EP80579 Datasheet, PDF (1366/1916 Pages) Intel Corporation – Intel® EP80579 Integrated Processor Product Line

Intel^® EP80579 Integrated Processor
Note:
The original (82542 compatible) descriptor will be referred to as the “legacy” descriptor
format and is described in “Legacy Transmit Descriptor Format” on page 1366. The two
new descriptor types are collectively referred to as extended descriptors. One of the
new descriptor types is quite similar to the legacy descriptor in that it points to a block
of packet data. This descriptor type is called the TCP/IP Data Descriptor and is offered
as a replacement for the legacy descriptor since it offers access to new off loading
capabilities. The other new descriptor type is fundamentally different as it does not
point to packet data. It merely contains control information which are loaded into
registers of the GbE and affect the processing of future packets. The following
paragraphs describe the three descriptor formats.
The extended descriptor types are accessed by setting the TDESC.DEXT bit to 1. If this
bit is set, the TDESC.DTYP field is examined to control the interpretation of the
remaining bits of the descriptor. Figure 37-16 shows the generic layout for all extended
descriptors. Fields marked as NR are not reserved for any particular function and are
defined on a per-descriptor type basis. Notice that the DEXT and DTYP fields are non-
contiguous in order to accommodate legacy mode operation. For legacy mode
operation, bit 29 is set to 0 and the descriptor is defined as described in “Legacy
Transmit Descriptor Format” on page 1366.
Figure 37-16.Transmit Descriptor (TDESC) Layout
63
30 29 28
24 23
20 19
0
0
Not-Reserved[63:0]
8
NR
DEXT
NR
DTYP
NR
37.5.6.3 Legacy Transmit Descriptor Format
To select legacy (82542 compatible) mode operation, bit 29 (TDESC.DEXT) should be
set to 0. In this case, the descriptor format is defined as shown in Figure 37-17.
Address and length must be supplied by software. Bits in the command byte are
optional, as are the CSO, and CSS fields.
Figure 37-17.Legacy Transmit Descriptor (TDESC) Layout
63
48 47 40 39 36 35 32 31 24 23 16 15
0
0
Buffer Address[63:0]
8
Special
CSS
Rsvd
STATUS
CMD
CSO
Length
Length (TDESC.LENGTH) specifies the length in bytes to be fetched from the buffer
address provided. The maximum length associated with any single legacy descriptor is
16288 bytes. Although a buffer as short as one byte is allowed, the total length of the
packet, before padding and CRC insertion, must be at least 17 bytes.
Note:
The maximum allowable packet size for transmits changes based on the value written
to the Packet Buffer Allocation Register, whose settings can modify the size of the
transmit FIFO.
Descriptor length(s) may be further limited by the size of the transmit FIFO. Due to the
need to support optional checksum calculation & insertion, all buffers comprising a
single packet must be able to be stored simultaneously in the transmit FIFO. For any
individual packet, the sum of the individual descriptor lengths must be at least 80 bytes
less than the allocated size of the transmit FIFO.
Intel^® EP80579 Integrated Processor Product Line Datasheet
1366
August 2009
Order Number: 320066-003US