COM20020I-DZD-TR Standard Microsystems (SMSC), COM20020I-DZD-TR Datasheet - Page 22

• Manufacturer Part Number: COM20020I-DZD-TR
• Manufacturer: Standard Microsystems (SMSC)

Specifications of COM20020I-DZD-TR

• Number Of Transceivers: 1
• Operating Supply Voltage (max): 5.5V
• Operating Supply Voltage (typ): 5V
• Operating Supply Voltage (min): 4.5V
• Operating Temperature (max): 85C
• Operating Temperature (min): -40C
• Operating Temperature Classification: Industrial
• Mounting: Surface Mount
• Pin Count: 28
• Lead Free Status / RoHS Status: Compliant

Revision 12-05-06
media (not on each individual node). The nPULSE1 signal, in this mode, is an open drain or push/pull
driver and is used to directly drive the media. It issues a 200nS negative pulse to transmit a logic "1". Note
that when used in the open-drain mode, the COM20020ID does not have a fail/safe input on the RXIN pin.
The nPULSE1 signal actually contains a weak pull-up resistor. This pull-up should not take the place of
the resistor required on the media for open drain mode.
In typical applications, the serial backplane is terminated at both ends and a bias is provided by the
external pull-up resistor.
The RXIN signal is directly connected to the cable via an internal Schmitt trigger. A negative pulse on this
input indicates a logic "1". Lack of pulse indicates a logic "0". For typical single-ended backplane
applications, RXIN is connected to nPULSE1 to make the serial backplane data line. A ground line (from
the coax or twisted pair) should run in parallel with the signal. For applications requiring different treatment
75176B or
Equiv.
RT
20MHZ
CLOCK
(FOR REF.
ONLY)
nPULSE1
nPULSE2
DIPULSE
RXIN
Figure 5.4 - COM20020ID Network Using RS-485 Differential Transceivers
COM20020ID
100ns
Figure 5.5 – Dipulse Waveform for Data of 1-1-0
200ns
100ns
400ns
1
DATASHEET
RBIAS
+VCC
COM20020ID
Page 22
+VCC
5Mbps ARCNET (ANSI 878.1) Controller with 2K x 8 On-Chip RAM
1
RBIAS
COM20020ID
+VCC
0
SMSC COM20020I Rev D
RBIAS
RT
Datasheet