TNETE2004

MDIO-MANAGED QuadPHY

FOUR 10BASE-T PHYSICAL-LAYER INTERFACES

SPWS023D – OCTOBER 1996 – REVISED OCTOBER 1997

13

POST OFFICE BOX 655303

link test

When not in auto-negotiation mode, the PHY sends link pulses, separated by an interval of 16 ms, on the

data-out (DO) circuit. The receiver looks for valid link pulses on the input pair. If a link pulse is not received within

a given time interval, the device enters a link-fail state. In this state, link pulses continue to be generated, and

the receiver constantly looks for the link-pulse pattern. The device remains in this state until a valid receive

packet or multiple legal link-test pulses are received.

loopback test mode

By asserting the LOOPBACK pin on the device or by setting the LOOPBACK bit in the PHY generic control

register, the transmit circuit of each PHY is looped to the corresponding receive circuit closest to the twisted-pair

I/O pins. Thereafter, transmit drivers do not forward any further packet data but continue to send link-test pulses.

When accessing loopback test mode from the package pins, since there is only one LOOPBACK pin on the

package, all four PHYs are placed in LOOPBACK mode simultaneously. Individual PHYs can be placed in

LOOPBACK mode by means of the TNETE2004 registers. While in LOOPBACK mode, all receive activities,

other than link-test pulses, are ignored. However, squelch information is still processed, allowing the link status

to be maintained under momentary loopback self-test.

LED status indication

The TNETE2004 has 12 pins that drive LEDs. Each PHY has the following three status LEDs:

Note: The LEDs are all off when reset is active. Once reset is inactive, all the LEDs turn on for 100ms, then turn

off, and then function in the normal way. The following signals are active low.

LEDxLINK –

illuminates when PHYx has established a valid link

LEDxACTIVE – illuminates when PHYx is transmitting or receiving data. This LED illuminates for a minimum

duration of 20 ms for each activity, but if packets are being received or transmitted faster than

20 ms, it stays on continuously.

LEDxDUPCOL – illuminates continuously when PHYx is in full-duplex mode. Illuminates for a minimum

duration of 20 ms when collisions occur in half-duplex mode. Additionally, in half-duplex

mode, LED0DUPCOL–LED3DUPCOL flashes when a jabber condition is detected. This

feature is not available in full-duplex mode.

IEEE Std 1149.1 (JTAG) test port

Compliant with the IEEE Std 1149.1, the test-access port is composed of five pins. These pins interface serially

with the device and the board on which the device is installed for boundary-scan testing. The TNETE2004

implements the following JTAG instructions:

000

EXTEST

External boundary-scan test

001

SAMPLE/PRELOAD

Initialization for boundary-scan test

100

IDCODE

Scans out TNETE2004 identification code

101

HIGHZ

Sets all digital output pins on the TNETE2004 to high impedance

111

BYPASS

Connects 1-bit bypass register between TDI and TDO