TNETX3150 Datasheet, PDF (27/113 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
uplink frame RX routing via post tagging (continued)
tag 0
BIT 7
Destination
Port 08
10 Mbit/s
BIT 6
Destination
Port 07
10 Mbit/s
BIT 5
Destination
Port 06
10 Mbit/s
BIT 4
Destination
Port 05
10 Mbit/s
BIT 3
Destination
Port 04
10 Mbit/s
BIT 2
Destination
Port 03
10 Mbit/s
BIT 1
Destination
Port 02
10/100 Mbit/s
BIT 0
Destination
Port 01
10/100 Mbit/s
tag 1
BIT 7
BIT 6
Reserved
BIT 5
Destination
Port 14
10 Mbit/s
BIT 4
Destination
Port 13
10 Mbit/s
BIT 3
Destination
Port 12
10 Mbit/s
BIT 2
Destination
Port 11
10 Mbit/s
BIT 1
Destination
Port 10
10 Mbit/s
BIT 0
Destination
Port 09
10 Mbit/s
tag 2
BIT 7
Reserved
BIT 0
tag 3
BIT 7
Reserved
BIT 0
Figure 9. Tag-Field Coding
If only one bit is set in the destination port field, the packet is sent to a single port. For example, with
tag 0 = 00000000 and tag 1 = xx000100, the packet is unicast and destined for port 11.
If more than one bit is set, the packet is sent to multiple ports. For example, with tag 0 = 11001010 and
tag 1 = xx001001, the packet is transmitted from ports 12, 09, 08, 07, 04, and 02. This allows broadcast and
multicast traffic to be limited in supporting external VLANs.
If all bits are clear in the tags, the packet is invalid and is discarded.
NOTE:
The four tag fields do not immediately follow the frame data, but are presented after the end of data
(following an idle period), and require that M00RXDVX = 1 and M00RXDV = 1.
uplink flow control
Flow control is available only on the uplink port and is applicable in full-duplex mode only. In this mode, asserting
the collision signal before the TNETX3150/TNETX3150A begins the transmission of a frame forces the
TNETX3150/TNETX3150A to wait for the collision signal to be deasserted before the frame is transmitted. The
collision pin is sampled immediately before transmission. If it is not asserted, frame transmission continues. If
the collision signal is asserted after transmission, the current frame continues to be transmitted. The
TNETX3150/TNETX3150A delays all future-frame transmissions until the collision signal is deasserted. The
interfacing hardware must be capable of storing up to a maximum-length Ethernet frame to prevent dropping
frames due to congestion.
The frame is transmitted immediately following the deassertion of the collision signal. The
flow-control-requesting device must be ready to accept data when the collision signal is deasserted following
a flow-controlled frame. No interframe gap is imposed by the TNETX3150/TNETX3150A in this mode of
operation. This provides maximum flexibility and control to the interfacing hardware on the uplink.
• POST OFFICE BOX 655303 DALLAS, TEXAS 75265
27