TNETX3150 Datasheet, PDF (44/113 Pages) Texas Instruments – ThunderSWITCHE 15-PORT 10-/100-MBIT/S ETHERNETE SWITCH

TNETX3150/TNETX3150A
ThunderSWITCH^™ 15-PORT 10-/100-MBIT/S ETHERNET^™ SWITCH
SPWS027F – FEBRUARY 1997 – REVISED SEPTEMBER 1997
port-N address registers at 0x8*N + 0x0002 through 0x8*N + 0x0007 (N = port number in hex)
+2
+3
+4
+5
+6
+7
Port address (47–0)
These six byte-wide registers hold the port’s assigned source address, and are used to control address
assignment and security for the port. Together, these six registers contain a 47-bit IEEE Std 802-specific MAC
address and a security enable bit. This bit is in the address group/specific (G/S) bit. The G/S bit is the first bit
of address from the wire, but because of the least-significant bit-first addressing Ethernet scheme, this
corresponds to the least-significant bit of the first byte, or address bit 40.
The security enable bit (port address 40) is used to indicate the use of secure addressing on a port. In the secure
addressing mode, once an address is assigned to a port, that source address can be used only with that port,
and that port only with that source address. Use of that source address on another port causes it to be
suspended or disabled. Use of a different source address on the secured port causes it to be suspended or
disabled.
The uplink port (port 00) does not have a port address. The port address registers for port 00 (DIO addresses
0x0002–0x0007) cannot be written and are always read as zero.
An address can be assigned to a port in two different ways: explicitly or dynamically. An address is explicitly
assigned by writing it to the port address registers. An address is assigned dynamically by the
TNETX3150/TNETX3150A hardware loading the register from the source address field of received frames. If
a port is in secured mode, the address is loaded only once from the first received frame. In unsecured mode,
the address is updated on every frame received. (TNETX3150/TNETX3150A never assigns a duplicate port
address. If the address is securely assigned to another port, then this port is placed in an unaddressed state
– the address is set to zero – null address. If the address is assigned to another port, but not securely, then the
other port is placed in an unaddressed state.)
D Writing 0x00.00.00.00.00.00 to the registers places the port in an unsecured, unaddressed state.
D Writing 0x01.00.00.00.00.00 to the registers places the port in a secured, unaddressed state.
D Writing a non-zero address (with bit 40 clear) sets the port address in an unsecured state.
D Writing a non-zero address (with bit 40 set) sets the port address in a secured state.
To prevent dynamic updating of the port address during DIO writes to the address registers, (which would create
a corrupt address), dynamic updating is disabled by writes to the first address register (47–40) and reenabled
by writes to the last address register (7–0). Ensure that all six bytes are always written and in the correct order.
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