TNETX15VE datasheet(81/113 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

FIND, FINDFIRST, FINDNEXT, and FINDNEW commands (continued)

The NEW bit is asserted by the ADD logic operation. The FIND logic operation clears this bit after giving the

address to management. The steps for scanning the whole table for all NEW addresses is as follows:

• Perform a FINDNEW command by:

• Setting the NEW bit in the findcontrol register. No write to findnode is required. The

TNETX15VE scans the lookup table for the first NEW address from the beginning of the table

each time NEW is set.

• Waiting until the FNDCPLT interrupt is asserted [FNDCPLT (bit 6) in interrupt register] or poll

findcontrol until the register bits are cleared

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

address and information are placed in the registers. The NEW flag in the address is cleared. If

FOUND is not set, an address was not found and the lookup table contains no NEW addresses.

• Since the FIND command clears the NEW bit, looking for the next NEW address means repeating the

FINDNEW command until no more addresses are found. The NEW bit is cleared on all FIND

commands. Always check the NEW bit (7) in the findport register (0x12–0x13 DIO) on non-NEW finds.

• NEW is automatically set with a wire add; the host can set the state of the NEW bit with an add/edit

command.

VLAN and PORT find modifier bits

The VLAN and PORT bits in the findcontrol register are used with the NEW, FIRST, NEXT, and LKUP bits to

modify the FIND operations.

The PORT bit limits the FINDFIRST, FINDNEXT, and FIND commands to look for only the addresses whose

port assignment matches the port contained in the portcode field of findport. This command is useful when

management wants to know all addresses that are associated with a port number. Since only unicast addresses

can be matched to a port (multicasts use a port bit mask), using the PORT modifier limits returns to unicast

addresses. To dump all unicast addresses associated with port 01, the user must:

• Write a 0x01 to the most-significant bit of findport (portcode = 0x1)

• Perform a FINDFIRST port command by:

• Setting the PORT and FIRST bits in the findcontrol register. No write to findnode and

findVLANID is required. The TNETX15VE scans the lookup table for the first address that is

associated with port 01.

• WaitinguntiltheFNDCPLTinterruptisasserted,orpollfindcontroluntiltheFIRSTbitiscleared.

The PORT bit stays set.

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

address and information are placed in the registers. If FOUND is not set, and an address was

not found, there are no more addresses associated with this port.

TNETX15VE 数据表(PDF) 81 Page - Texas Instruments

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