PCI Express System Architecture

ACK/NAK DLLP Format

The format of an ACK or NAK DLLP is illustrated in Figure 5-6 on page 219. Table 5-6 describes the ACK or NAK DLLP Fields.

Figure 5-6. Ack Or Nak DLLP Packet Format

Table 5-1. Ack or Nak DLLP Fields

Field Name	Header Byte/Bit	DLLP Function
AckNak_Seq_Num [11:0]	Byte 3 Bit 7:0 Byte 2 Bit 3:0	For an ACK DLLP: For good TLPs received with Sequence Number = NEXT_RCV_SEQ count (count before incrementing), use NEXT_RCV_SEQ count - 1 (count after incrementing minus 1). For TLP received with Sequence Number earlier than NEXT_RCV_SEQ count (duplicate TLP), use NEXT_RCV_SEQ count - 1. For a NAK DLLP: Associated with a TLP that fails the CRC ...