78Q2120C
10/100BASE-TX
Transceiver
LED INDICATORS
The LED pins use standard logic drivers. They output a logic low when the LED is meant to be on and a logic
high when it is meant to be off. The LED should be connected in series with a resistor between the output pin and
the power supply.
NAME
LEDL
PIN
40
39
38
37
TYPE DESCRIPTION
CO
CO
CO
CO
LED LINK: ON for link up.
LED TRANSMIT: ON when there is a transmission (normally OFF).
LED RECEIVE: ON when there is a reception (normally OFF).
LED COLLISION: In half duplex mode, this is a collision indicator and turns ON
when a collision occurs. In full duplex mode, this LED is held OFF.
LEDTX
LEDRX
LEDCOL
LEDBTX
LEDBT
36
48
49
CO
CO
CO
LED 100BASE-TX: ON for 100BASE-TX connection and OFF for other
connections. LEDBTX is OFF during auto-negotiation.
LED 10BASE-T: ON for 10BASE-T connection and OFF for other
connections. LEDBTis OFF during auto-negotiation.
LEDFDX
LED FULL DUPLEX: ON when in full duplex mode and OFF when in half
duplex mode.
OSCILLATOR/CLOCK
NAME
CKIN
PIN
4
TYPE DESCRIPTION
CIS
CLOCK INPUT: Connects to a 25 MHz TTL compatible clock source. This
pin should be held low when XTLP and XTLN are being used as the 25 MHz
clock source.
XTLP/N
59,58
A
CRYSTAL PINS: Should be connected to a 25 MHz crystal. When CKIN is
being used as the 25 MHz clock source, these pins should be left floating or
connected together.
MISCELLANEOUS PIN
NAME
INTR
PIN
35
TYPE DESCRIPTION
COZ INTERRUPT PIN: This pin is used to signal an interrupt to the media access
controller. The pin is held in the high impedance state when an interrupt is
not indicated. The pin will be forced high or low to signal an interrupt
depending upon the value of the INPOL bit (MR16.14). The events which
trigger an interrupt can be programmed via the Interrupt Control Register
located at address MR17.
NC
54,56
--
No Connect. Do not connect to ground or supply.
POWER SUPPLY AND GROUND
NAME
PIN
TYPE DESCRIPTION
VCC
8,11,41,
43,57,63
S
3.3V SUPPLY
GND
3,5,9,10,
G
GROUND
42,53,55,60
Page: 9 of 35
© 2009 Teridian Semiconductor Corporation
Rev 1.3
TERIDIAN [ TERIDIAN SEMICONDUCTOR CORPORATION ]
