8101 datasheet(55/172 Pages) LSI

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Receive Status Word

2-37

2.14 Receive Status Word

A 32-bit status word can be appended to the end of each good receive

data packet and stored in the receive FIFO. This status word contains a

byte count and error information for the receive data packet.

2.14.1 Format

The format for the status word is shown in Table 2.11. The upper sixteen

bits contain the actual byte count for the packet and the lower sixteen

bits contain the status information related to the packet. Note that the

endian select bit affects the byte order of the status word in the same

way that it affects the normal data byte order on the system interface.

The byte count value in the status word (upper sixteen bits) is the total

number of actual bytes in the received packet minus the preamble, SFD,

and CRC bytes. The byte count is independent of whether the receive

MAC has stripped the preamble or CRC. If the packet overﬂows the

receive FIFO, the byte count stops counting at the moment that the

receive FIFO overﬂow has been detected and the remaining bytes on the

incoming packet are not counted.

Table 2.11

Receive Status Word Deﬁnition

RXD31

RXD16

BC[15:0]

RXD15

RXD0

RESERVED

MPKT

CWRD

OSIZE USIZE OVFL

CRC

Symbol

Name

Deﬁnition

Position on

RXD[31:0]1

BC[15:0]

Byte count

Contains actual byte count of the receive packet

RXD[31:16]

–

Reserved

RXD[15:6]

MPKT

Multiple packet

reject

1 = RX FIFO full and multiple consecutive packets

were discarded. Status word indicates error

condition for ﬁrst packet of discarded group.

RXD5

CWRD

Codeword error

1 = Receive packet has PCS coding error

RXD4

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