XRT94L31 datasheet(21/133 Pages) EXAR

21 / 133 page

XRT94L31

REV. 1.0.1

3-CHANNEL DS3/E3/STS-1 TO STS-3/STM-1 MAPPER IC

TxTOH

TTL

Transmit TOH Input Port - Input pin:

This input pin, along with the TxTOHIns input pin, the TxTOHEnable and

TxTOHFrame and TxTOHClk output pins function as the Transmit TOH

Input Port.To externally insert user values of TOH into the outbound

STS-3 data stream via the Transmit TOH Input Port, do the following.

• Continuously sample the state of TxTOHFrame and TxTOHEnable

upon the rising edge of TxTOHClk

• Whenever TxTOHEnable pulses "High", then the user's external

circuitry should drive the TxTOHIns input pin "High"

• Next, output the next TOH bit, onto this input pin, upon the rising edge

of TxTOHClk. The Transmit TOH Input Port will sample the data (on

this input pin) upon the falling edge of TxTOHClk.

NOTE: Data at this input pin will be ignored (e.g., not sampled) unless

the TxTOHEnable output pin is "High" and the TxTOHIns input

pin is pulled "High".

TxTOHFrame

CMOS

Transmit TOH Input Port - STS-3/STM-1 Frame Indicator:

This output pin, along with TxTOHClk, TxTOHEnable output pins, and

the TxTOH and TxTOHIns input pins function as the Transmit TOH Input

Port.This output pin will pulse "High" (for one period of TxTOHClk), one

TxTOHClk clock period prior to the first TOH bit of a given STS-3 frame,

being expected via the TxTOH input pin.To externally insert user values

of TOH into the outbound STS-3 data stream via the Transmit TOH Input

Port, do the following.

• Continuously sample the state of TxTOHEnable and this output pin

upon the rising edge of TxTOHClk.

• Whenever the TxTOHEnable output pin pulse "High", then the user's

external circuitry should drive the TxTOHIns input pin "High".

• Next, output the next TOH bit, onto the TxTOH input pin, upon the

rising edge of TxTOHClk.

NOTE: The external circuitry (which is being interfaced to the Transmit

TOH Input Port can use this particular output pin to denote the

boundary of STS-3 frames.

PIN DESCRIPTION OF THE XRT94L31 (REV. B)

PIN #

SIGNAL NAME

I/O

TYPE

DESCRIPTION

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