Frame Descriptor Format - Motorola MC68824 User Manual

DISPLACEMENT
(IN BYTES)
DESCRIPTION OF FIELD
a
CONFIRMATION/INDICATION WORD
2 RECEIVE STATUS WORD
4 CONTROL FOR NEXT FD POINTER
6 NEXT FD POINTER - HIGH
8 NEXT FD POINTER - LOW
A RESERVED
C FIRST BD POINTER - HIGH
E FIRST BD POINTER - LOW
10
FRAME DATA LENGTH
12 RESERVED
14 RESERVED
16 IR FRAME DESCIRPTOR POINTER - HIGH
18 IR FRAME DESCRIPTOR POINTER - LOW
lA RESERVED
lB FRAME CONTROL - BYTE
IF ALEN
=
a
THEN THE ADDRESS LENGTH IS 2 BYTES
lC MAC DESTINATION ADDRESS - LEAST SIGNIFICANT BYTE
10 MAC DESTINATION ADDRESS - MOST SIGNIFICANT BYTE
IE
MAC SOURCE ADDRESS - LEAST SIGNIFICANT BYTE
IF MAC SOURCE ADDRESS - MOST SIGNIFICANT BYTE
20
RESERVED
22
RESERVED
IF ALEN
=
1 THEN THE ADDRESS LENGTH IS 6 BYTES
lC MAC DESTINATION ADDRESS - BYTE
a
IEEE LSB
10 MAC DESTINATION ADDRESS - BYTE 1
IE MAC DESTINATION ADDRESS - BYTE 2
IF MAC DESTINATION ADDRESS - BYTE 3
20
MAC DESTINATION ADDRESS - BYTE 4
21
MAC DESTINATION ADDRESS - BYTE 5
22 MAC SOURCE ADDRESS - BYTE
a
23 MAC SOURCE ADDRESS - BYTE 1 IEEE LSB
24 MAC SOURCE ADDRESS - BYTE 2
25 MAC SOURCE ADDRESS - BYTE 3
26 MAC SOURCE ADDRESS - BYTE 4
27 MAC SOURCE ADDRESS - BYTE 5
28 RESERVED
2A
RESERVED
Figure 4-3. Frame Descriptor Format
4.1.1.1 FD CONFIRMATION/INDICATION WORD FORMAT. The first word of the frame descriptor
contains the frame descriptor confirmation/indication word. This word holds status information
of the frame and the queue. The frame descriptor confirmation word must be cleared by the host
before being placed into the free frame descriptor pool or the transmit queue. This word is used
in both transmission and reception queues and is updated by the TBC.
The format of this word for a TRANSMISSION queue is shown below:
F E D C B A 9 8 7 6 5 4 3
a
I
CFD
I
N/P
I
EMP
I
FTL
I
RES
I
UR
I
NR
I
UF
I
RT7
I
RT6
I
RT5
I
RT4
I
RT3
I
AT2 ATI RTO
CFD - Confirm Frame Descriptor
o
Frame has not yet been processed (remaining indication bits are meaningless in this word)
1 TBC completed processing of this frame
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