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XRT79L71
PRELIMINARY
39
1-CHANNEL DS3/E3 CLEAR-CHANNEL FRAMERLIU COMBO - CC/HDLC ARCHITECTURE
REV. P2.0.0
TABLE 6: THE ROLES OF VARIOUS MICROPROCESSOR INTERFACE PINS, WHEN CONFIGURED TO OPERATE IN THE
POWERPC 403 MODE
PIN NAME
PIN/BALL
NUMBER
TYPE
DESCRIPTION
ALE/AS
A16
I
No Function - Tie to GND:
RD/DS/WE
C15
I
Write Enable Input - WE
If the Microprocessor Interface is operating in the Power PC 403 Mode,
then this input pin will function as the WE (Write Enable) input pin.
Anytime the Microprocessor Interface samples this active-low input sig-
nal (along with
CS and WR/R/W) also being asserted (at a logic low
level) upon the rising edge of
PCLK, then the Microprocessor Interface
will (upon the very same rising edge of
PCLK) latch the contents on the
Bi-Directional Data Bus (D[7:0]) into the "target" on-chip register or buffer
location within the XRT79L71.
RDY/DTACK/RDY
C14
O
Active High READY Output - RDY
If the Microprocessor Interface has been configured to operate in the
Power PC 403 Mode, then this output pin will function as the "active-
high" READY output.
During a READ or WRITE cycle, the Microprocessor Interface block will
toggle this output pin to the logic high level, ONLY when it (the Micropro-
cessor Interface) is ready to complete or terminate the current READ or
WRITE cycle. Once the Microprocessor has sampled this signal being at
the logic "high" level (upon the rising edge of PCLK), 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 "low" level, then the Microprocessor is
expected to extend this READ or WRITE cycle, until it samples this out-
put pin being at the logic low level.
NOTE: The Microprocessor Interface will update the state of this output
pin upon the rising edge of
PCLK.
PCLK
H16
I
Microprocessor Interface Clock Input:
This clock input signal is only used if the Microprocessor Interface has
been configured to operate in one of the Synchronous Modes (e.g.,
Power PC 403 Mode). If the Microprocessor Interface is configured to
operate in one of these modes, then it will use this clock signal to do the
following.
To sample the CS, WR/R/W, A[14:0], D[7:0], RD/DS and DBEN input
pins, and
To update the state of the D[7:0] and the RDY/DTACK output signals.
NOTE: The Microprocessor Interface can work with
PCLK frequencies
ranging up to 33MHz.