SMSC LAN1198 Manual De Usuario
LAN9118 Family Programmer Reference Guide
Revision 1.0 (12-14-09)
30
SMSC AN 12.12
APPLICATION NOTE
6.5 Transmit Packet Examples
Let’s take a look at
, which shows a 78-byte (0x4e) transmit
packet used in the example, which begins at location 0xb4002013 in physical memory. In this case,
it happens to be an IP packet to be sent from our MAC source address of 00:80:0f:71:55:71 to a
destination MAC address of 00:0e:83:a0:de:ff.
it happens to be an IP packet to be sent from our MAC source address of 00:80:0f:71:55:71 to a
destination MAC address of 00:0e:83:a0:de:ff.
In a PIO type transfer, 4-byte DWORD values are copied from memory to the device TX_DATA_FIFO,
so we begin building the TX_CMD_A command word by setting the Buffer End Alignment field to
0x0 to indicate 4-byte alignment:
so we begin building the TX_CMD_A command word by setting the Buffer End Alignment field to
0x0 to indicate 4-byte alignment:
Then, use the 2 low-bits from of the physical address (0x3) to set the 5-bit Data Start Offset field,
since we are only transferring 4 bytes at a time (PIO). Also we want to transfer the entire packet in
a single buffer transfer action, so First Segment and Last Segment flags are both set.
since we are only transferring 4 bytes at a time (PIO). Also we want to transfer the entire packet in
a single buffer transfer action, so First Segment and Last Segment flags are both set.
In the TX_CMD_B command word, we use a unique value of 0x1234 for the Packet Tag field, and an
overall Packet Length the same as the Buffer Size as the entire packet is transfer in a single action.
Note that the Buffer Size refers to the individual transfer payload, not counting the offset and padding
alignment, but in this simple case, length and size are the same.
overall Packet Length the same as the Buffer Size as the entire packet is transfer in a single action.
Note that the Buffer Size refers to the individual transfer payload, not counting the offset and padding
alignment, but in this simple case, length and size are the same.
Table 6.2 Transmit Packet Example
PHYSICAL MEMORY
0XB4002000
0x0
0x1
0x2
0x3
0x4
0x5
0x6
0x7
0x8
0x9
0xa
0xb
0xc
0xd
0xe
0xf
0x00
0x10
XX
XX
XX
00
0e
83
a0
de
ff
00
80
0f
71
55
71
08
0x20
00
45
00
00
28
11
56
40
00
80
06
f0
6a
aa
81
50
0x30
76
aa
81
53
96
04
e7
01
bd
a9
4a
38
0d
0a
d6
7c
0x40
6c
50
10
Ff
ff
f9
29
00
00
66
6f
72
53
4d
53
43
0x50
4d
2e
20
44
62
76
69
64
20
47
65
4c
62
6d
61
6e
0x60
21
YY
YY
YY
0x70
0x80
Table 6.3 Buffer End Alignment
ALIGNMENT REQUIREMENT
VALUE (25:24)
4-word alignment
0x0
16-word alignment
0x1
32-word alignment
0x2
(undefined, illegal)
0x3
TX_CMD_A
31
30
29
28
27
26
Buffer
End
Alignment
23
22
21
Data
Start
Offset
15
14
First
Segment
Last
Segment
11
Buffer
Size
0x0
0x3
1
1
0x4e