Intel NETWORK PROCESSOR IXP2800 - Manual (Page 266)

266 Hardware Reference Manual
Intel
®
IXP2800 Network Processor
Media and Switch Fabric Interface
8.3.2.1 SPI-4
For SPI-4, data is put into the data portion of the element, and information for the SPI-4 Control
Word that will precede the data is put into the Element Control Word.
When the Element Control Word is written the information is (the data comes from two
consecutive Transfer registers; bits [31:0] from the lower numbered and bits[63:32] from the
higher numbered):
The definitions of the fields are shown in Table 98 .
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
9 8 7 6 5 4 3 2 1 0
Payload Length
Prepend
Offset
Prepend Length
Payload
Offset
Res Sk
ip Abort SOP EOP
ADR
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
Res
Table 98. TBUF SPI-4 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. That
value will also control the EOPS field (1 or 2 bytes valid indicated) of the Control Word
that will succeed the data transfer. Note
1 .
Prepend Offset Indicates the first valid byte of Prepend, from 0 to 7, as defined in Section 8.3.2 .
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, as defined in Section 8.3.2 .
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.
Abort
Indicates if the element is the end of a packet that should be aborted. If this bit is set, the
status code of EOP Abort will be sent in the EOPS field of the Control Word that will
succeed the data transfer. Note
1 .
SOP
Indicates if the element is the start of a packet. This field will be sent in the SOPC field of
the Control Word that will precede the data transfer.
EOP
Indicates if the element is the end of a packet. This field will be sent in the EOPS field of
the Control Word that will succeed the data transfer. Note
1 .
ADR
The port number to which the data is directed. This field will be sent in the ADR field of the
Control Word that will precede the data transfer.
NOTE:
1. Normally EOPS is sent on the next Control Word (along with ADR and SOP) to start the next element. If
there is no valid element pending at the end of sending the data, the transmit logic will insert an Idle Control
Word with the EOPS information.