COM20020 Datasheet, PDF (6/72 Pages) SMSC Corporation – COM20020 3.3V ULANC Universal Local Area Network Controller with 2K x 8 On-Board RAM

DIP PIN
NO.
16,15
PLCC PIN
NO.
19,18
NAME
nPulse 2,
nPulse 1
17
20
Receive In
18
21
nTransmit
nEnable
13,14
16,17
Crystal
Oscillator
24
15,28
Power
Supply
12
7,14,22 Ground
SYMBOL
nPULSE2,
nPULSE1
RXIN
nTXEN
XTAL1,
XTAL2
VDD
DESCRIPTION
Output (nPULSE1), Input/Output (nPULSE2).
In Normal Mode, these active low signals
carry the transmit data information, encoded
in pulse format, as DIPULSE waveform.
When the device is in Backplane Mode, the
nPULSE1 signal driver is programmable
(push/pull or open-drain), while the nPULSE2
signal provides a clock with frequency of
double the data rate. nPULSE1 is connected
to a weak internal pull-up resistor on the
open/drain driver in backplane mode.
Input. This signal carries the receive data
information from the line tranceiver.
Output. This signal is used prior to the Power-
up to enable the line drivers for transmission.
The polarity of the signal is programmable
through the nPULSE2 pin.
nPULSE2 floating before Power-up: nTXEN
active low (Default option)
nPULSE2 grounded before Power-up:
nTXEN active high (This option is only
available in Backplane Mode)
An external crystal should be connected to
these pins. Oscillation frequency range is
from 10 to 20 MHz. If an external TTL clock is
used instead, it must be connected to XTAL1
with a 390! pull-up resistor, and XTAL2
should be left floating.
+3.3 Volt Power Supply pin.
VSS
Ground pin.
6