Single-Chip Ethernet Controller with HP Auto-MDIX Support and PCI Interface

 

Datasheet

 

Table 3.5 RDES0 Bit Fields (continued)

 

 

BITS

DESCRIPTION

 

 

29:16

FL - Frame Length

 

Indicates the length in bytes, including the CRC, of the received frame that was transferred to

 

Host memory. This field is set only after the last descriptor (LS) bit is set and the descriptor error

 

(DE) is reset.

 

Host Actions: Reads this field to determine Frame Length.

 

DMAC Actions: Initializes this field to define Frame Length.

 

 

15

ES - Error Summary

 

Indicates the logical OR of the following RDES0 bits:

 

RDES0[1] - CRC error

 

RDES0[6] - Collision seen

 

RDES0[7] - Frame too long

 

RDES0[11] - Runt frame

 

RDES0[14] - Descriptor Error

 

Host Actions: Checks this bit to determine status.

 

DMAC Actions: Sets/clears this bit to define status.

 

 

14

DE - Descriptor Error

 

When set, indicates a frame truncation caused by a frame that does not fit within the current

 

descriptor buffers, and that the DMA controller does not own the next descriptor. The frame is

 

truncated. This field is set only after the last descriptor (LS) bit is set.

 

Host Actions: Checks this bit to determine status.

 

DMAC Actions: Sets/clears this bit to define status.

 

 

13

RESERVED

 

Host Actions: Cleared on writes and ignored on reads.

 

DMAC Actions: Ignored on reads and cleared on writes.

 

 

12

LE - Length Error

 

When set, this bit indicates that the actual length does not match with the Length/Type field of

 

the incoming frame.

 

Host Actions: Checks this bit to determine status.

 

DMAC Actions: Sets/clears this bit to define status.

 

 

11

RF - 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 memory only if the Pass Bad Frames bit

 

(PASS_BAD) in the MAC control register (MAC_CR) is set.

 

Host Actions: Checks this bit to determine status.

 

DMAC Actions: Sets/clears this bit to define status.

 

 

10

MF - Multicast Frame

 

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

 

Host Actions: Checks this bit to determine status.

 

DMAC Actions: Sets/clears this bit to define status.

 

 

9

FS - First Descriptor

 

When set, indicates that this descriptor contains the first buffer of a frame. If the size of the first

 

buffer is 0, the second buffer contains the beginning of the frame. If the size of the second buffer

 

is also 0, the second descriptor contains the beginning of the frame.

 

Host Actions: Checks this bit to determine status.

 

DMAC Actions: Sets/clears this bit to define status.

 

 

8

LS - Last Descriptor

 

When set, indicates that the buffers pointed to by this descriptor are the last buffers of the frame.

 

Host Actions: Checks this bit to determine status.

 

DMAC Actions: Sets/clears this bit to define status.

 

 

Revision 1.22 (09-25-08)

42

SMSC LAN9420/LAN9420i

 

DATASHEET