XRT79L71_07 Datasheet, PDF (9/109 Pages) Exar Corporation – 1-CHANNEL DS3/E3 ATM UNI/PPP/CLEAR-CHANNEL FRAMER IC - HARDWARE

REV. 1.0.0
PIN DESCRIPTIONS
PIN #
A16
NAME
ALE/AS
D14
CS
D13
INT
XRT79L71
1-CHANNEL DS3/E3 ATM UNI/PPP/CLEAR-CHANNEL FRAMER IC - HARDWARE
TYPE
DESCRIPTION
I Address Latch Enable/Address Strobe:
The exact function of this input pin depends upon which mode the Microprocessor
Interface has been configured to operate in.
Intel-Asynchronous Mode - ALE
If the Microprocessor Interface of the XRT79L71 has been configured to operate in
the Intel-Asynchronous Mode, then this active-"High" input pin is used to latch the
address (present at the Microprocessor Interface Address Bus pins (A[14:0]) into the
XRT79L71 Microprocessor Interface block and to indicate the start of a READ or
WRITE cycle.
Pulling this input pin "High" enables the input bus drivers for the Address Bus input
pins (A[14:0]). The contents of the Address Bus will be latched into the XRT79L71
Microprocessor Interface circuitry, upon the falling edge of this input signal.
Motorola-Asynchronous (68K) Mode - AS
If the Microprocessor Interface has been configured to operate in the Motorola-Asyn-
chronous Mode, then this active-"Low" input pin is used to latch the data (residing on
the Address Bus, A[14:0]) into the Microprocessor Interface circuitry of the
XRT79L71.
Pulling this input pin "Low" enables the input bus drivers for the Address Bus input
pins. The contents of the Address Bus will be latched into the Microprocessor Inter-
face circuitry, upon the rising edge of this signal.
Power PC 403 Mode - No Function - Tie to GND:
If the Microprocessor Interface has been configured to operate in the Power PC 403
Mode, then this input pin has no role nor function and should be tied to GND.
I Chip Select Input:
The user must assert this active "Low" signal in order to select the Microprocessor
Interface for READ and WRITE operations between the Microprocessor and the
XRT79L71 on-chip registers and buffer/memory locations.
O Interrupt Request Output:
This active-"Low" output signal will be asserted when the XRT79L71 is requesting
interrupt service from the Microprocessor. This output pin should typically be con-
nected to the Interrupt Request input of the Microprocessor.
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