Intel NETWORK PROCESSOR IXP2800 - Manual (Page 244)

244 Hardware Reference Manual
Intel
®
IXP2800 Network Processor
Media and Switch Fabric Interface
Control words are inserted only between burst transfers; once a transfer has begun, data words are
sent uninterrupted until either End of Packet or a multiple of 16 bytes is reached. The order of bytes
within the SPI-4 data burst is shown in Table 84 .
The most significant bits of the bytes correspond to bits 15 and 7. On data transfers that do not end
on an even byte-boundary, the unused byte on bits [7:0] is set to all zeros.
Table 83. SPI-4 Control Word Format
Bit
Position
Label Description
15 Type
Control Word Type.
• 1—payload control word (payload transfer will immediately follow the control word).
• 0—idle or training control word.
14:13 EOPS
End-of-Packet (EOP) Status.
Set to the following values below according to the status of the immediately preceding
payload transfer.
• 00—Not an EOP.
• 01—EOP Abort (application-specific error condition).
• 10—EOP Normal termination, 2 bytes valid.
• 11—EOP Normal termination, 1 byte valid.
EOPS is valid in the first Control Word following a burst transfer. It is ignored and set to 00
otherwise.
12 SOP
Start-of-Packet (SOP).
• Set to 1 if the payload transfer immediately following the Control Word corresponds to
the start of a packet; set to 0 otherwise.
• Set to 0 in all idle and training control words.
11:4 ADR
Port Address.
8-bit port address of the payload data transfer immediately following the Control Word.
None of the addresses are reserved (all are available for payload transfer).
• Set to all zeros in all idle Control Words.
• Set to all ones in all training Control Words.
3:0 DIP-4
4-bit Diagonal Interleaved Parity.
4-bit odd parity computed over the current Control Word and the immediately preceding
data words (if any) following the last Control Word.