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Hardware Reference Manual 67
Intel
®
IXP2800 Network Processor
Technical Description
2.7.4.1.2 CSIX and TBUF
For CSIX, payload information is put into the data area of the element, and Base and Extension
Header information is put into the Element Control Word.
When the Element Control Word is written, the information is:
The definitions of the fields are shown in Table 16.
2.7.4.2 Transmit Operation Summary
During transmit processing data to be transmitted is placed into the TBUF under Microengine
control. The Microengine allocates an element in software; the transmit hardware processes TBUF
elements within a partition in strict sequential order so the software can track which element to
allocate next.
Microengines may write directly into an element by an
msf[write] instruction, or have data from
DRAM written into the element by a
dram[tbuf_wr] instruction. Data can be merged into the
element by doing both.
3
1
3
0
2
9
2
8
2
7
2
6
2
5
2
4
2
3
2
2
2
1
2
0
1
9
1
8
1
7
1
6
1
5
1
4
1
3
1
2
1
1
1
0
9876543210
Payload Length
Prepend
Offset
Prepend Length
Payload
Offset
Res
Skip
Res
CR
P
Res Type
6
3
6
2
6
1
6
0
5
9
5
8
5
7
5
6
5
5
5
4
5
3
5
2
5
1
5
0
4
9
4
8
4
7
4
6
4
5
4
4
4
3
4
2
4
1
4
0
3
9
3
8
3
7
3
6
3
5
3
4
3
3
3
2
Extension Header
Table 16. TBUF CSIX Control Definition
Field Definition
Payload Length
Indicates the number of Payload bytes, from 1 to 256, in the element. The value of 0x00
means 256 bytes. The sum of Prepend Length and Payload Length will be sent, and also
put into the CSIX Base Header Payload Length field. Note that this length does not
include any padding that may be required. Padding is inserted by transmit hardware as
needed.
Prepend Offset Indicates the first valid byte of Prepend, from 0 to 7.
Prepend Length Indicates the number of bytes in Prepend, from 0 to 31.
Payload Offset Indicates the first valid byte of Payload, from 0 to 7.
Skip
Allows software to allocate a TBUF element and then not transmit any data from it.
0—transmit data according to other fields of Control Word.
1—free the element without transmitting any data.
CR CR (CSIX Reserved) bit to put into the CSIX Base Header.
P P (Private) bit to put into the CSIX Base Header.
Type Type Field to put into the CSIX Base Header. Idle type is not legal here.
Extension Header
The Extension Header to be sent with the CFrame. The bytes are sent in big-endian
order; byte 0 is in bits 63:56, byte 1 is in bits 55:48, byte 2 is in bits 47:40, and byte 3 is in
bits 39:32.