User manual

254 Hardware Reference Manual
Intel
®
IXP2800 Network Processor
Media and Switch Fabric Interface
Note: In CSIX protocol, an RBUF element is allocated only on RxSof assertion. Therefore, the element
size must be programmed based on the Switch Fabric usage. For example, if the switch never sends
a payload greater than 128 bytes, then 128-byte elements can be selected. Otherwise, 256-byte
elements must be selected.
Data received from the bus is placed into the element lowest-offset first in big-endian order
(that is, with the first byte received in the most significant byte of the 32-bit word, etc.).
The status contains the following information:
The definitions of the fields are shown in Table 91.
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
RPROT
Element Payload Length
CR
P
Err
Len Err
HP Err
VP Err
Null
Reserved 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 91. RBUF CSIX Status Definition
Field Definition
RPROT
This bit is a 1, indicating that the Status is for CSIX-L1. It is derived from the RPROT input
signal.
Element
The element number in the RBUF that holds the data. This is equal to the offset in RBUF
of the first byte in the element, shifted right by six places.
Payload Length Payload Length Field from the CSIX Base Header. A value of 0x0 indicates 256 bytes.
CR CR (CSIX Reserved) bit from the CSIX Base Header.
P P (Private) bit from the CSIX Base Header.
Err Error. This is the logical OR of VP Err, HP Err, and Len Err.
Len Err
Length Error; either
amount of Payload received (before receipt of next Base Header) did not match value
indicated in Base Header Payload Length field) or
Payload Length field was greater than size of RBUF element.
HP Err Horizontal Parity Error was detected on the CFrame. See description in Section 8.2.8.2.1.
VP Err Vertical Parity Error was detected on the CFrame. See description in Section 8.2.8.2.2.
Null
Null receive. If this bit is set, it means that the Rx_Thread_Freelist timeout expired
before any more data was received, and that a null Receive Status Word is being pushed,
to keep the receive pipeline flowing. The rest of the fields in the Receive Status Word
must be ignored; there is no data or RBUF entry associated with a null Receive Status
Word.
Type Type Field from the CSIX Base Header.
Extension Header
The Extension Header from the CFrame. The bytes are received 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.