TNETX15VE datasheet(79/113 Pages) TI1

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TNETX15VE

VLAN-ENGINE ADDRESS-LOOKUP DEVICE

SPWS028B – APRIL 1997 – REVISED SEPTEMBER 1997

POST OFFICE BOX 655303

• DALLAS, TEXAS 75265

PRINCIPLES OF OPERATION

management-based lookups (FIND)

The FIND logic operation is designed to give the programmer a simple way to find addresses within the lookup

table. The FIND logic operation is controlled from the following internal registers:

BYTE 3

BYTE 2

BYTE 1

BYTE 0

DIO ADDRESS

FindVLANID

0x08

Findnode23–Findnode16

Findnode31–Findnode24

Findnode39–Findnode32

Findnode47–Findnode40

0x0C

Findport

Findnode7–Findnode0

Findnode15–Findnode8

0x10

Findcontrol

Findnodeage

0x14

The interface provides: 48-bit read or writeable register findnode in which the address is placed; a VLANID

is placed; and a 16-bit register findnodeage, which contains the age time stamp of the node being looked up.

FIND, FINDFIRST, FINDNEXT, and FINDNEW commands

Four FIND commands can be modified by PORT or VLAN bits: FINDFIRST, FINDNEXT, FIND(LKUP), and

FINDNEW. These are used to interrogate the table that the TNETX15VE built as a result of all ADDS. Without

the modifiers, FIND works on all addresses; each modifier applied reduces the pool. Applying VLAN and PORT

results in an address that matches that VLAN and that PORT.

Also classed as a FIND is FINDNBKR (the interrogation of the FIFO storing and address/port information for

packets that overrode the receive block barrier). Showing the value on the top of the FIFO pops it off.

FINDNEW looks for addresses that still have their NEW bit set. Finding an address with the NEW bit set results

in the NEW bit being cleared. Every FINDNEW operation starts at the beginning of the table. It does not affect

the operation of the FINDNEW to load or leave an address in the findnode registers (0xC–0x11).

The logic performs the command given to it, and indicates that it has stopped looking for the address by

asserting the FNDCPLT bit in the int register. If the FNDCPLT bit in the intmask register is set to a 1, this gives

an interrupt to the host. Another way FIND indicates completion is by clearing its command bits. The findcontrol

a 0x01 to findcontrol (LKUP) then this register reads 0x01 until the FIND logic operation is finished operating.

If an address is found as a result of the command just completed, it is indicated by asserting the FOUND bit in

findcontrol. The FOUND bit indicates that the information in the findnode, findVLANID, findport, and

findnodeage registers is valid.

The FIND command finds a specific user-defined address in the lookup table. The procedure for the FIND

command is as follows:

• Write the 48-bit address query in the findnode register and the node’s 2-bit VLANID in findVLANID.

• Set the LKUP bit in the findcontrol register. The TNETX15VE scans the lookup table for that particular

address.

• Poll the findcontrol register until the LKUP bit is cleared. Since a LKUP is very quick, only a few polling

cycles are required. No interrupt is given for LKUP-operations completing.

• Read the findcontrol register. If FOUND is set, the address was found and the node’s information is

placed in the registers. If FOUND is not set, the address was not found within the lookup table.

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