XRT72L53 Datasheet, PDF(266/467 Page) Exar Corporation – THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER

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XRT72L53 Datasheet, PDF (266/467 Pages) Exar Corporation – THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER

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PRELIMINARY

XRT72L53

THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER

REV. P1.1.8

3. Interface the XRT72L53, to the Terminal Equip-

ment, as illustrated in Figure 106.

NOTE: The XRT72L53 Framer IC cannot support the

Framer Local Loop-back Mode of operation, while operating

in Mode 4. The user must configure the XRT72L53 Framer

IC into any of the following modes prior to configuring the

Framer Local Loop-back Mode operation.

â¢ Mode 2 - Serial/Local-Timed/Frame-Slave Mode

â¢ Mode 3 - Serial/Local-Timed/Frame-Master Mode

â¢ Mode 5 - Nibble-Parallel/Local-Timed/Frame-Slave

Mode

â¢ Mode 6 - Nibble-Parallel/Local-Timed/Frame-Mas-

ter Mode.

For more detailed information on the Framer Local

Loop-back Mode, please see Section 6.0.

5.2.1.5 Mode 5 - The Nibble-Parallel/Local-

Timed/Frame-Slave Interface Mode Behavior of

the XRT72L53

If the XRT72L53 has been configured to operate in

this mode, then the XRT72L53 will function as fol-

lows:

A. Local-Timed - Uses the TxInClk signal as the

Timing Reference

In this mode, the Transmit Section of the XRT72L53

will use the TxInClk signal at its timing reference. Fur-

ther, the chip will internally divide the TxInClk clock

signal by a factor of 4 and will output this divided

clock signal via the TxNibClk output pin. The Transmit

Terminal Equipment Input Interface block (within the

XRT72L53) will use the rising edge of the TxNibClk

signal, to latch the data, residing on the TxNib[3:0] in-

to its circuitry.

B. Nibble-Parallel Mode

The XRT72L53 will accept the E3 payload data, from

the Terminal Equipment, in a parallel manner, via the

TxNib[3:0] input pins. The Transmit Terminal Equip-

ment Input Interface will latch this data into its circuit-

ry, on the rising edge of the TxNibClk output signal.

C. Delineation of outbound E3 Frames

The Transmit Section will use the TxInClk input signal

as its timing reference and will use the TxFrameRef

input signal as its Framing Reference (e.g., the Trans-

mit Section of the XRT72L53 initiates frame genera-

tion upon the rising edge of the TxFrameRef signal).

D. Sampling of payload data, from the Terminal

Equipment

In Mode 5, the XRT72L53 will sample the data, at the

TxNib[3:0] input pins, on the third rising edge of the

TxInClk clock signal, following a pulse in the TxNibClk

signal (see Figure 108).

NOTE: The TxNibClk signal, from the XRT72L53 operates

nominally at 8.592 MHz (e.g., 34.368 MHz divided by 4).

Interfacing the Transmit Payload Data Input Inter-

face block of the XRT72L53 to the Terminal Equip-

ment for Mode 5 Operation

Figure 108 presents an illustration of the Transmit

Payload Data Input Interface block (within the

XRT72L53) being interfaced to the Terminal Equip-

ment, for Mode 5 Operation.

FIGURE 108. ILLUSTRATION OF THE TERMINAL EQUIPMENT BEING INTERFACED TO THE TRANSMIT PAYLOAD DATA

INPUT INTERFACE BLOCK OF THE XRT72L53 FOR MODE 5 (NIBBLE-PARALLEL/LOCAL-TIMED/FRAME-SLAVE) OPER-

ATION

E3_Nib_Clock_In

E3_Data_Out[3:0]

Tx_Start_of_Frame

E3_Overhead_Ind

34.368MHz Clock Source

8.592MHz

4

TxInClk

TxNibClk

NibInt

TxNib[3:0]

TxFrameRef

TxOH_Ind

VCC

Terminal Equipment

XRT72L5x E3 Framer

266

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