Chapter 12: 10/100 IEEE802.3 Media Access Controller
TX7901 User’s Manual (Rev. 6.30T – Nov, 2001)
12-35
12.3.4.1 Perfect
Table
The Perfect Table holds 16 destination addresses (full 48-bit MAC addresses). The MAC
compares the addresses of any incoming frame to these addresses, and also checks the
status of the Receive Frame Configuration Register. It rejects addresses that:
Do not match if inverse filtering is reset.
Match if inverse filtering is set.
This table should be filled with valid MAC addresses. Any mix of physical and multicast
addresses can be used. Unused addresses should reset the PAValid bit, and reset bit 63 to
zero. If none of the PAValid bits is set, the MAC works in the promiscuous mode.
Note:
These tables can only be written to when reception is disabled.
Addresses are contained in the lower 48 bits, as per the following table:
Table 12-33 Perfect Table Field Descriptions
Bit(s)
Field
Description
63
PAValid
When set, indicates that this physical address is valid. It is
used for address filtering
62:48
–
Reserved
47:0
PA
Physical Address (PA5:PA4:PA3:PA2:PA1:PA0)
63
62
48
47
40 39
32 31
24 23
16 15
8 7
0
V
0
PA5
PA4
PA3
PA2
PA1
PA0
1
15
8
8
8
8
8
8
12.3.4.2 Hash
Table
The Hash Table process is used in individual and group hash filtering. It stores 512 bits that
serve as hash bucket heads, and one physical 48-bit MAC address. This process can be
used in two different ways:
1. Incoming frames with multicast destination addresses are subjected to imperfect filtering.
Frames with physical addresses are checked against the single physical address (see
Figure 12-5.)
For any incoming frame with a multicast destination address, the MAC applies the standard
Ethernet cyclic redundancy check (CRC) function to the first 6 bytes containing the
destination address, then uses the most significant 9 bits of the result as a bit index in the
table. If the indexed bit is set, the frame is accepted. If the bit is cleared, the frame is
rejected.
2. All incoming frame destination addresses go to the Hash Table. The MAC uses the
same method as above to get the indexed bit. If the indexed bit is set, the frame is
accepted. If the bit is cleared, the frame is rejected.
Summary of Contents for TMPR7901
Page 1: ...TX System RISC TX79 Family TMPR7901 Symmetric 2 way superscalar 64 bit CPU ...
Page 14: ...Handling Precautions ...
Page 15: ......
Page 17: ...1 Using Toshiba Semiconductors Safely 1 2 ...
Page 41: ...4 Precautions and Usage Considerations 4 2 ...
Page 42: ...TX7901 User s Manual Rev 6 30T November 2001 DOCUMENT NUMBER M 99 00004 07 ...
Page 43: ......
Page 259: ...Chapter 13 Removed TX7901 User s Manual Rev 6 30T Nov 2001 13 1 13 Removed ...
Page 260: ...Chapter 13 Removed TX7901 User s Manual Rev 6 30T Nov 2001 13 2 ...