MOTOROLA
Chapter 6. Programming Model
6-5
PRELIMINARYÑSUBJECT TO CHANGE WITHOUT NOTICE
Table 6-5 describes HASH_TABLE_LOW Þelds.
6.2.5 Beginning of RxBD Ring (R_DES_START)
The R_DES_START register, shown in Figure 6-5, is like the RBASE register used by
other protocols. It provides a pointer to the start of the circular RxBD queue in external
memory. This pointer should be quad-word aligned. Bits 30 and 31 should be written to 0
by the user; hardware ignores non-zero values in these bits. This register is written by the
user, is not reset, and must be initialized by the user.
Table 6-6 describes R_DES_START Þelds.
6.2.6 Beginning of TxBD Ring (X_DES_START)
The X_DES_START register, shown in Figure 6-6, is like the TBASE register used by other
protocols. It provides a pointer to the start of the circular TxBD queue in external memory.
This pointer should be quad-word aligned. Bits 30 and 31 should be cleared by the user;
hardware ignores non-zero values in these bits. It is written by the user, is not reset, and
must be initialized by the user.
Table 6-5. HASH_TABLE_LOW Field Descriptions
Bits
Name
Description
0Ð31
HASH_LOW Contains the lower 32 bits of the 64-bit hash table used in address recognition for receive
frames with a multicast address. HASH_LOW[0] contains hash index bit 31. HASH_LOW[31]
contains hash index bit 0.
Bits
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Field
R_DES_START
Reset
UndeÞned
R/W
Read/write
Addr
0xE10
Bits
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
Field
R_DES_START
00
Reset
UndeÞned
R/W
Read/write
Addr
0xE12
Figure 6-5. R_DES_START Register
Table 6-6. R_DES_START Field Descriptions
Bits
Name
Description
0Ð29
R_DES_START
Pointer to start of RxBD queue.
30Ð31
Ñ
Reserved. Should be written to zero by the host processor.
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