COM20019I datasheet(9/65 Pages) SMSC

9 / 65 page

Low Cost ARCNET (ANSI 878.1) Controller with 2K x 8 On-Board RAM

SMSC COM20019I

Page 9

Rev. 04-15-05

DATASHEET

PLCC PIN

NO.

NAME

SYMBOL

DESCRIPTION

TRANSMISSION MEDIA INTERFACE

19,18

nPulse 2,

nPulse 1

nPULSE2,

nPULSE1

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. The COM20019I

does not support the Normal Mode. Use only

in the Backplane Mode.

Receive In

RXIN

Input. This signal carries the receive data

information from the line transceiver.

nTransmit

nEnable

nTXEN

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)

16,17

Crystal

Oscillator

XTAL1,

XTAL2

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.

15,28

Power

Supply

VDD

+5 Volt Power Supply pin.

7,14,22

Ground

VSS

Ground pin.

COM20019I Datasheet(PDF) 9 Page - SMSC Corporation

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