XRT79L71 datasheet(10/109 Pages) EXAR

10 / 109 page

XRT79L71

1-CHANNEL DS3/E3 ATM UNI/PPP/CLEAR-CHANNEL FRAMER IC - HARDWARE

REV. 1.0.0

C15

RD/DS/WE

READ Strobe/Data Strobe:

The exact function of this input pin depends upon which mode the Microprocessor

Interface has been configured to operate in.

Intel-Asynchronous Mode - RD - READ Strobe Input:

If the Microprocessor Interface is operating in the Intel-Asynchronous Mode, then

this input pin functions as the RD (Active "Low" Read Strobe) input signal from the

Microprocessor. Once this active-"Low" signal is asserted, then the XRT79L71

places the contents of the addressed register or buffer location on the Microproces-

sor Interface Bi-directional data bus (D[7:0]). When this signal is negated, then the

Data Bus is tri-stated.

Motorola-Asynchronous (68K) Mode - DS - Data Strobe:

If the Microprocessor Interface is operating in the Motorola-Asynchronous Mode,

then this input pin functions as the DS (Data Strobe) input signal.

Power PC 403 Mode - WE - Write Enable Input:

If the Microprocessor Interface is operating in the Power PC 403 Mode, then this

input pin functions as the WE (Write Enable) input pin.

Anytime the Microprocessor Interface samples this active-"Low" input signal (along

with CS and WR/R/W) also being asserted at a logic "Low" level upon the rising edge

of mPCLK, then the Microprocessor Interface will (upon the very same rising edge of

mPCLK) latch the contents on the Bi-Directional Data Bus (D[7:0]) into the target on-

chip register or buffer location within the XRT79L71.

PIN DESCRIPTIONS

PIN #NAME

TYPE

DESCRIPTION

XRT79L71 Datasheet(PDF) 10 Page - Exar Corporation