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XRT79L71
PRELIMINARY
31
1-CHANNEL DS3/E3 CLEAR-CHANNEL FRAMERLIU COMBO - CC/HDLC ARCHITECTURE
REV. P2.0.0
TABLE 4: THE ROLES OF VARIOUS MICROPROCESSOR INTERFACE PINS, WHEN CONFIGURED TO OPERATE IN THE
INTEL-ASYNCHRONOUS MODE
PIN NAME
PIN/BALL
NUMBER
TYPE
DESCRIPTION
ALE/AS
A16
I
Address Latch Enable Input - ALE
If the Microprocessor Interface has been configured to operate in the
Intel-Asynchronous 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 Interface circuitry, upon the falling edge of this input sig-
nal.
RD/DS/WE
C15
I
Read Strobe Input - RD
If the Microprocessor Interface is operating in the Intel-Asynchronous
Mode, then this input pin will function as the RD (Active Low Read Strobe)
input signal from the Microprocessor. Once this active-low signal is
asserted, then the XRT79L71 will place the contents of the addressed
register (or buffer location) on the Microprocessor Interface Bi-directional
data bus (D[7:0]). When this signal is negated, then the Data Bus will be
tri-stated.
RDY/DTACK/RDY
C14
O
Active Low Ready Output - RDY
If the Microprocessor Interface has been configured to operate in the
Intel-Asynchronous Mode, then this output pin will function as the "active-
low" READY output.
During a READ or WRITE cycle, the Microprocessor Interface block will
toggle this output pin to the logic low level, ONLY when it (the Micropro-
cessor Interface) is ready to complete or terminate the current READ or
WRITE cycle. Once the Microprocessor has determined that this input
pin has toggled to the logic "low" level, then it is now safe for it to move on
and execute the next READ or WRITE cycle.
If (during a READ or WRITE cycle) the Microprocessor Interface block is
holding this output pin at a logic "high" level, then the Microprocessor is
expected to extend this READ or WRITE cycle, until it detects this output
pin being toggled to the logic low level.
PCLK
H16
I
NONE - Tie to GND
WR/R/W
B16
I
Write Strobe Input - WR
If the Microprocessor Interface is configured to operate in the Intel-Asyn-
chronous Mode, then this input pin functions as the WR (Active Low
WRITE Strobe) input signal from the Microprocessor. Once this active-
low signal is asserted, then the input buffers (associated with the Bi-
Directional Data Bus pin, D[7:0]) will be enabled. The Microprocessor
Interface will latch the contents on the Bi-Directional Data Bus (into the
"target" register or address location, within the XRT79L71) upon the rising
edge of this input pin.