SMSC LAN9420 - Manual (Page 42)

Single-Chip Ethernet Controller with HP Auto-MDIX Support and PCI Interface
Datasheet
Revision 1.22 (09-25-08) 42 SMSC LAN9420/LAN9420i
DATASHEET
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.
Table 3.5 RDES0 Bit Fields (continued)
BITS DESCRIPTION