XRT4500CV datasheet(63/99 Pages) EXAR

63 / 99 page

XRT4500

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MULTIPROTOCOL SERIAL NETWORK INTERFACE IC

REV. 1.0.7

If the user enables the Internal Oscillator, within the

XRT4500, then the XRT4500 will output between a

32kHz and a 64kHz clock signal via the RX2D and

RX3D signals. When the XRT4500 is interfaced to the

DTE SCC, this translates into the XRT4500 generating

the timing signals for “TXC” and the “RXC” input signals.

As a consequence, the DTE SCC is provided with all of

the requisite timing signals that it would normally have, if

it were interfaced to a DCE Terminal. This feature per-

mits the user to implement a wide variety of diagnostic

programs for DTE Equipment stand-alone testing.

NOTE: The Internal Oscillator feature is only available if the

XRT4500 has been configured to operate in the DTE Mode.

1.3.10 Glitch Filters

Occasional extraneous glitches on control/handshake

signal inputs such as CTS, RTS, DTR and DSR can

have damaging effects on the integrity of a connection.

The XRT4500 is equipped with lowpass filters on the

input of each of the receivers for the control and

handshake signals. These filters eliminate glitches

which are narrower than 10µs. The user may disable

these filters by setting EN_FLTR to logic 0.

1.3.11 Data Inversion

Similar to TXC, there is a provision in the XRT4500 to

invert the TXD and RXD signals. Once the Setting

the DTINV* input to logic 0 enables an inverter at the

output of RX1 and input of TX1.

1.3.12 Data Interlude

Similar to TXC, there is a provision in the XRT4500 to

invert the TXD and RXD signals. Once the Setting the

DTINV* input to logic 0 enables an inverter at the out-

put of RX1 and input of TX1.

2.0

RECEIVER AND TRANSMITTER

SPECIFICATIONS

Table 3 and Table 4, which are for the XRT4500 re-

ceiver and transmitter sections respectively, summa-

rize the electrical requirements for V.35, V.11, V.10,

and RS232 interfaces. These tables provide virtually

all of the electrical information necessary to describe

these 4 interfaces in a concise form.

3.0

V.10\V.28 OUTPUT PULSE RISE AND FALL

TIME CONTROL

SLEW_CNTL (pin 47) is an analog output that con-

trols transmitter pulse rise and fall time for the V.10

and V.28 modes. Connecting a resistor, RSLEW, hav-

ing a value between 0 and 200 k

Ω from this pin to

ground controls the rise/fall times for V.10 and the

slew rate for V.28 as shown in Figure 34 and

Figure 35 respectively.

FIGURE 33. ILLUSTRATION OF THE INTERNAL OSCILLATORS WITHIN THE XRT4500

SCC (L)

XRT4500

RX1

RX2

RX3

TX2

TX1

TXD

SCTE

TXC_IN

RXC_IN

RXD_IN

TXD

SCTE

TXC

RXC

RXD

OSC

DTE

XRT4500CV Datasheet(PDF) 63 Page - Exar Corporation

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