TNETX3270
ThunderSWITCH 24/3 ETHERNET SWITCH
WITH 24 10-MBIT/S PORTS AND 3 10-/100-MBIT/S PORTS
SPWS043B – NOVEMBER 1997 – REVISED APRIL 1999
7
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
Terminal Functions (Continued)

10-Mbit/s MAC multiplexed interface (ports 00–23) is multiplexed into three groups (TH0, TH1, and

TH2) of eight ports† (continued)

TERMINAL
I/O
INTERNAL
DESCRIPTION
NAME NO.
I/O
RESISTOR
DESCRIPTION
TH0TXD3
TH0TXD2
TH0TXD1
TH0TXD0
TH1TXD3
TH1TXD2
TH1TXD1
TH1TXD0
TH2TXD3
TH2TXD2
TH2TXD1
TH2TXD0
218
217
216
215
239
237
236
234
20
19
18
16
O None
Interface transmit data. The transmit data nibble for the current port is synchronous to
THxCLK. When THxTXEN is asserted, these signals carry data. THxTXD3–THxTXD0 are
used during renegotiation to convey flow-control and duplex configuration requests to the
PHY. THxTXD0 is the least significant bit and THxTXD3 is the most significant bit.
TH0RXDV
TH1RXDV
TH2RXDV
226
6
26 I Pulldown Interface receive data valid. When THxRXDV is a 1, it indicates that the THxRXD lines contain
valid data.
†THx = TH0, TH1, and TH2
10-/100-Mbit/s MAC interface (ports 24–26)‡
TERMINAL
I/O
INTERNAL
DESCRIPTION
NAME NO.
I/O
RESISTOR
DESCRIPTION
M24COL
M25COL
M26COL
42
65
90 I Pulldown Collision sense. Assertion of MxxCOL in half-duplex signal indicates a network collision
on that port. In full-duplex operation, transmission of new frames does not start if this
terminal is asserted.
M24CRS
M25CRS
M26CRS
43
66
92 I Pulldown Carrier sense. MxxCRS indicates a frame carrier signal is being received.
M24FORCE10
M25FORCE10
M26FORCE10
54
80
104 I/O§Pullup
Speed selection (force 10 Mbit/s is active low)
– If pulled low by either the TNETX3270 or a PHY, the port operates at 10 Mbit/s.
– If not pulled low by either the TNETX3270 or a PHY, the internal pullup resistor holds
this signal high and the port operates at 100 Mbit/s. An external 4.7-kΩ pullup resistor
connected to VDD(3.3V) may be required, depending on the system layout.
M24LINK
M25LINK
M26LINK
52
78
102 I Pulldown
Connection status. MxxLINK indicates the presence of a port connection.
– If MxxLINK = 0, there is no link.
– If MxxLINK = 1, the link is good.
M24FORCEHD
M25FORCEHD
M26FORCEHD
53
79
103 I/O‡Pullup
Duplex selection (force half duplex is active low)
– If pulled low by either the TNETX3270 or the PHY, the port operates at half duplex.
– If not pulled low by either the TNETX3270 or the PHY, the internal pullup resistor holds
this signal high and the port operates at full duplex. An external 4.7-kΩ pullup resistor
connected to VDD(3.3V) may be required, depending on the system layout.
M24RCLK
M25RCLK
M26RCLK
44
67
93 I Pullup Receive clock. Receive clock source from the attached PHY or PMI device.
‡xx = ports 24, 25, and 26
§Not a true bidirectional terminal. It can only be actively pulled down (open drain).