XRT4500 datasheet(21/99 Pages) EXAR

21 / 99 page

XRT4500

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MULTIPROTOCOL SERIAL NETWORK INTERFACE IC

REV. 1.0.7

PIN DESCRIPTIONS (CONT.)

Signal

DTE

MODE

DCE

MODE

TYPE

FUNCTION

OSCEN

Test Oscillator Enable – Active Low;

This active-low input pin permits the user to enable or disable the

“Internal Oscillator” within the XRT4500. If the user enables this fea-

ture then the XRT4500 will begin generating a clock signal via both

the RX2D and RX3D output pins. The frequency of this clock signal

ranges between 32kHz and 64kHz.

This clock signal can be used to support “Stand-Alone DTE Diag-

nostic” Testing.

Setting this input to “0” enables the “Internal Oscillator”.

Setting this input to “1” disables the “Internal Oscillator”.

Note: The “Internal Oscillator” is only available if the XRT4500 is

operating in the DTE Mode.

If LP = “0” The Clock Signal (32 - 64kHz) is available on Rx3D.

If LP = “0” and EC = “0” the clock signal is available on RX2D.

NOTE: This input pin contains an internal 20k

Ω pull-up to V

DD.

CLKINV

Invert Clock Input Pin – This ‘Active -Low’ input pin permits the

user to either enable or disable the ‘Clock/Inversion’ feature. The

exact manifestation of the ‘Clock Inversion’ feature depends upon

whether the XRT4500 is operating in the ‘DCE’ or ‘DTE’ Mode.

If the XRT4500 is operating in the DTE Mode, then the RX3D output

signal (which is receiving the TXC signal) will be inverted before it is

outputted to the terminal equipment.

If the XRT4500 is operating in the DCE Mode, then the TX3D input

signal (which is transmitting the TXC signal) will be inverted before it

converted into the analog format and is output to the line.

Setting this input pin ‘Low’ enables the ‘Clock Inversion’ feature.

Conversely, setting this input pin ‘High’ disables this feature.

NOTE: This input pin contains an internal 20k

Ω pull-up to V

DD.

DTINV

Invert Data – Active Low; Logic 0: Data Inverted.

Logic 1: Data not Inverted. Internal 20K

Ω pull-up V

DD.

VSS_T123

-6V Power Supply Signal: This supply voltage is internally gener-

ated by the Switching Regulator Circuit within the XRT4500.

GND

Digital Ground: for transmitters 1, 2, and 3

VDD_T123

Analog VDD: for transmitters 1, 2, and 3

GND_T12

Analog Ground: Transmitters 1 and 2

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