TNETX3150 datasheet(55/78 Pages) TI

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TNETX15AE

ADDRESS-LOOKUP DEVICE

SPWS041A – AUGUST 1997 – REVISED OCTOBER 1997

POST OFFICE BOX 655303

• DALLAS, TEXAS 75265

PRINCIPLES OF OPERATION

FIND, FINDFIRST, and FINDNEXT commands

There are three find commands supported by the TNETX15AE: FINDFIRST, FINDNEXT, and FIND(LKUP).

These are used to interrogate the table that the TNETX15AE built as a result of all ADDS. FIND works on all

addresses.

FIND indicates completion by clearing its command bits. The findcontrol register keeps the code that the user

has written until the process is complete. For example, if the user writes a 0x01 to findcontrol (LKUP) then this

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, 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:

D Write the 48-bit address query in the findnode register.

D Set the LKUP bit in the findcontrol register. The TNETX15AE scans the lookup table for that

particular address.

D Poll the findcontrol register until the LKUP bit is cleared. A single read is necessary as the SRDY is delayed

until the operation is complete.

D 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.

The FINDFIRST command finds the first address contained in the lookup table. The procedure for the

FINDFIRST command is as follows:

D Set the FIRST bit in the findcontrol register. No write to findnode or findport is required. The TNETX15AE

scans the lookup table for the first address.

D Poll the findcontrol register until the FIRST bit is cleared. A single read is necessary as the SRDY is delayed

until the operation is complete (up to 6.4

µs).

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

information is placed in the registers. If FOUND is not set, an address was not found, i.e., the lookup table

is empty.

The FINDNEXT command finds the next address from that contained in the findnode register. The user can

either write a value in findnode and find the next address or keep the current value and continue finding next

addresses. The procedure for the FINDNEXT command is as follows:

D Write the starting address in findnode (if desired) or keep the currently held address.

D Set the NEXT bit in findcontrol. The TNETX15AE scans the lookup table for the next address after the one

contained in findnode.

D Poll the findcontrol register until the NEXT bit is cleared. A single read is necessary as the SRDY is delayed

until the operation is complete (up to 6.4

µs).

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

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

lookup table is empty.

The commands can be combined sequentially to quickly read the whole address table. All that is required is a

FINDFIRST, followed by FINDNEXT commands, until no more addresses are found.

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