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

Datasheet

 

Table 3.9 TDES0 Bit Fields (continued)

 

 

BITS

DESCRIPTION

 

 

8

EC - Excessive Collision

 

When set, indicates that the transmission was aborted after 16 successive collisions while

 

attempting to transmit the current frame.

 

Host Actions: Checks this bit to determine status.

 

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

 

 

7

RESERVED

 

Host Actions: Cleared on writes and ignored on reads.

 

DMAC Actions: Ignored on reads and cleared on writes.

 

 

6:3

CC - Collision Count

 

This 4-bit counter indicates the number of collisions that occurred before the frame was transmitted.

 

Not valid when the excessive collisions bit (EC - TDES0[8]) is also set.

 

Host Actions: Reads this field to determine Collision Count.

 

DMAC Actions: Initializes this field to define Collision Count.

 

 

2

ED - Excessive Deferral

 

If the deferred bit is set in the control register, the setting of the Excessive Deferral bit indicates

 

that the transmission has ended because of deferral of over 24,288-bit times during transmission.

 

Host Actions: Checks this bit to determine status.

 

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

 

 

1

Reserved

 

 

0

DE - Deferred

 

When set, indicates that the DMA Controller had to defer while ready to transmit a frame because

 

the carrier was asserted.

 

Host Actions: Checks this bit to determine status.

 

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

 

 

 

Transmit Descriptor 1 (TDES1)

 

 

Table 3.10 TDES1 Bit Fields

 

 

 

BITS

 

DESCRIPTION

 

 

 

31

 

IC - Interrupt on Completion

 

 

When set, the DMA Controller sets transmit interrupt (TI - DMAC_STATUS[0]) after the present

 

 

frame has been transmitted. This field is valid only when last segment (LS - TDES1[30]) is set.

 

 

Host Actions: Initializes this bit.

 

 

DMAC Actions: Reads this bit to determine whether IOC should be asserted.

 

 

 

30

 

LS - Last Segment

 

 

When set, indicates that the buffer contains the last segment of a frame.

 

 

Host Actions: Initializes this bit.

 

 

DMAC Actions: Reads this bit to determine whether the buffer contains the last segment of a

 

 

frame.

 

 

 

29

 

FS - First Segment

 

 

When set, indicates that the buffer contains the first segment of a frame.

 

 

Host Actions: Initializes this bit.

 

 

DMAC Actions: Reads this bit to determine whether the buffer contains the first segment of a

 

 

frame.

 

 

 

SMSC LAN9420/LAN9420i

47

Revision 1.22 (09-25-08)

 

DATASHEET