XRT4500CV datasheet(62/99 Pages) EXAR

62 / 99 page

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XRT4500

MULTIPROTOCOL SERIAL NETWORK INTERFACE IC

REV. 1.0.7

A system design similar to that presented below in

Figure 32, will accomplish the exact same function/re-

lationship between another Multi-protocol Transceiver

IC and the SCC/Microprocessor.

1.3.9

The Internal Oscillator

The XRT4500 includes an “Internal Oscillator” that

can be used to support “DTE Stand-Alone Testing/

Diagnostics” operations.

The user can enable the “Internal Oscillator” feature

(within the XRT4500) by pulling the “OSC_EN” input

pin (pin 53) “low”. Conversely, the user can disable

the “Internal Oscillator” feature by pulling the

“OSC_EN” input pin “high”.

If the user enables this feature, then the XRT4500 will

synthesize a clock signal (of frequencies ranging from

32kHz to 64kHz). Further, this clock signal will be out-

put via the “RX2D” and the “RX3D” output pins. Fig-

ure 1.20 presents an illustration of the XRT4500

(while interfaced to the DTE SCC) when the Internal

Oscillator is enabled.

FIGURE 32. AN ILLUSTRATION OF THE NECESSARY GLUE LOGIC REQUIRED TO DESIGN A FEATURE SIMILAR TO THAT

OFFERED BY THE

“REGISTERED” MODE, WHEN USING A DIFFERENT MULTI-PROTOCOL SERIAL NETWORK INTERFACE IC

µC/µP

Serial

Network

Interface Device

DTR_Signal

DSR_Signal

RL_Signal

RI_Signal

D-Flip-Flops

Clock

CLK

Clock Source

DTE Mode

XRT4500CV Datasheet(PDF) 62 Page - Exar Corporation