COM20022ITQFP datasheet(28/83 Pages) SMSC

28 / 83 page

10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Board RAM

Datasheet

Rev. 08-18-03

Page 28

SMSC COM20022I

DATASHEET

Figure 5.8

- COM20022I Network Using RS-485 Differential Transceivers

Figure 5.9

- Dipulse Waveform for Data of 1-1-0

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

of the receive signal (like filtering or squelching), nPULSE1 and RXIN remain as independent pins.

External differential drivers/receivers for increased range and common mode noise rejection, for example,

would require the signals to be independent of one another. When the device is in Backplane Mode, the

clock provided by the nPULSE2 signal may be used for encoding the data into a different encoding

scheme or other synchronous operations needed on the serial data stream.

20MHZ

CLOCK

(FOR REF.

ONLY)

nPULSE1

nPULSE2

DIPULSE

RXIN

100ns

200ns

400ns

COM20022I

+VCC

RBIAS

+VCC

RBIAS

75176B or

Equiv.

COM20022ITQFP Datasheet(PDF) 28 Page - SMSC Corporation