LAN89218 datasheet(59/148 Pages) MICROCHIP

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DS60001255B-page 59

LAN89218

Figure 3-28 shows the RX packet format when the RX checksum is enabled. The RX checksum data appended to

the data payload is treated just as an additional 4-bytes within the RX Data FIFO. The RX checksum is enabled by

setting the RXCOE_EN bit in the COE_CR—Checksum Offload Engine Control Register. For more information on

the RX checksum refer to Section 3.6.1.

3.13.3

RX STATUS FORMAT

FIGURE 3-28:

RX PACKET FORMAT WITH RX CHECKSUM

Bits

Description

Reserved. This bit is reserved. Reads 0.

Filtering Fail. When set, this bit indicates that the associated frame failed the address recognizing filter-

ing.

29:16

Packet Length. The size, in bytes, of the corresponding received frame.

Error Status (ES). When set this bit indicates that the MIL has reported an error. This bit is the Internal

logical “or” of bits 11,7,6 and 1.

Reserved. These bits are reserved. Reads 0.

Broadcast Frame. When set, this bit indicates that the received frame has a Broadcast address.

Length Error (LE). When set, this bit indicates that the actual length does not match with the length/

type field of the received frame.

Runt Frame. When set, this bit indicates that frame was prematurely terminated before the collision

window (64 bytes). Runt frames are passed on to the host only if the Pass Bad Frames bit MAC_CR Bit

[16] is set.

Multicast Frame. When set, this bit indicates that the received frame has a Multicast address.

9:8

Reserved. These bits are reserved. Reads 0.

Frame Too Long. When set, this bit indicates that the frame length exceeds the maximum Ethernet

specification of 1518 bytes. This is only a frame too long indication and will not cause the frame recep-

tion to be truncated.

ofs + First Data DWORD

Last Data DWORD

Host Read

Order

1st

2nd

Last

Optional Pad DWORD0

Optional Pad DWORDn

Optional offset DWORD0

Optional offset DWORDn

Checksum

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