XRT4500CV datasheet(49/99 Pages) EXAR

49 / 99 page

XRT4500

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MULTIPROTOCOL SERIAL NETWORK INTERFACE IC

REV. 1.0.7

The DTE Terminal

The DTE Terminal is responsible for sourcing/gener-

ating all of the following signals.

• TXD - Transmit Data

• TXCE (or SCTE) - Transmit Clock Echo

• DTR - Data Terminal Ready

• RTS - Request to Send

• LL - Local Loop-back Indicator

• RL - Remote Loop-back Indicator

Further, the DTE Terminal is responsible for receiv-

ing/terminating all of the following signals.

• RXD - Receive Data

• TXC - Transmit Clock

• RXC - Receive Clock

• DSR - Data Set Ready

• DCD - Data Carrier Detect

• CTS - Clear-to-Send

• RI (Ring Indicator)

• TM (Test Mode Indicator).

Because of this, whenever the XRT4500 is configured

to operate in the “DTE” Mode, then the following con-

figuration conditions are “TRUE”.

• Two “high-speed” Transmitters are enabled, and

• Three “high-speed” Receivers are enabled.

• Four “low-speed” Transmitters are enabled, and

• Four “low-speed” Receivers are enabled.

Other Comments about DCE and DTE Equipment

Whenever DCE and DTE Equipment are interfaced to

each other, the DCE Equipment is typically the

source of all timing signals. The DTE Equipment will

typically function as a “Clock Slave”.

1.3.3

The LP - Loop-Back Enable/Disable

Select Pin

As mentioned earlier, the XRT4500 can be configured

to operate in the loop-back mode. Setting the “LP” in-

put pin “high” disables the loop-back mode (within the

XRT4500). Conversely, setting this input “low” config-

ures the XRT4500 to operate in the “TXD/RXD” loop-

back mode.

A detailed description of the “TXD/RXD” loop-back

Mode is presented below.

Behavior of DTE/DCE Mode Devices, when the

Loop-Back Mode is Disabled

Figure 17 presents an illustration of a DTE and DCE

Terminal interfaced to each other when no XRT4500

Loop-Back Mode has een configured.

FIGURE 17. ILLUSTRATION OF BOTH THE DTE AND DCE MODE XRT4500 OPERATING, WHEN THE LOOP-BACK

MODE IS DISABLED

DTE (#2)

SCC (L)

XRT4500

RX1

TX1

RX2

TX2

RX3

TX3

RX2

TX2

RX1

TX1

RXD

RXC

TXC

SCTE_IN

TXD_IN

TXD

SCTE

TXC_IN

RXC_IN

RXD_IN

TXD

TXC

RXC

RXD

SCC (R)

DTE (#1)*

SCTE

* Indicates scenario # from Table 8

XRT4500CV Datasheet(PDF) 49 Page - Exar Corporation

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