Low Cost ARCNET (ANSI 878.1) Controller with 2K x 8 On-Board RAM
PLCC PIN
NO.
19,18
NAME
SYMBOL
DESCRIPTION
nPulse 2,
nPulse 1
20
21
Receive In
nTransmit
nEnable
16,17
Crystal
Oscillator
15,28
7,14,22
Power
Supply
Ground
TRANSMISSION MEDIA INTERFACE
nPULSE2,
Output (nPULSE1), Input/Output (nPULSE2).
In Normal Mode, these active low signals carry
nPULSE1
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.
RXIN
Input. This signal carries the receive data
information from the line transceiver.
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)
XTAL1,
An external crystal should be connected to
these pins. Oscillation frequency range is from
XTAL2
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.
V
DD
+5 Volt Power Supply pin.
V
SS
Ground pin.
SMSC COM20019I
Page 9
Rev. 03-07-06
DATASHEET
SMSC [ SMSC CORPORATION ]
