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XRT79L71
PRELIMINARY
25
1-CHANNEL DS3/E3 CLEAR-CHANNEL FRAMERLIU COMBO - CC/HDLC ARCHITECTURE
REV. P2.0.0
ALE/AS
A16
I
Address Latch Enable/Address Strobe:
The function of this input pin depends upon which mode the Microprocessor
Interface has been configured to operate in, as described below.
Intel-Asynchronous Mode - ALE
If the Microprocessor Interface has been configured to operate in the Intel-Asyn-
chronous Mode, then this active-high input pin is used to latch the data (residing
on the Address Bus, A[14:0]) into the Microprocessor Interface circuitry of the
XRT79L71 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.
The contents of the Address Bus will be latched into the Microprocessor Inter-
face 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-
Asynchronous 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 Micropro-
cessor Interface circuitry, upon the rising edge of this input 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.
CS
D14
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.
INT
D13
O
Interrupt Request Output:
This active-low output signal will be asserted (pulled to a logic low level) when-
ever the XRT79L71 is requesting interrupt service from the Microprocessor.
This output pin should typically be connected to the "Interrupt Request" input of
the Microprocessor.
Table 3: List and Brief Description of the Microprocessor Interface Pins
PIN NAME
PIN/BALL
NUMBER
TYPE
DESCRIPTION