Freescale Semiconductor POWERPC MPC860T - Manual (Page 37)

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.
30Р31 С Reserved. Should be written to zero by the host processor.
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