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XRT79L71
PRELIMINARY
27
1-CHANNEL DS3/E3 CLEAR-CHANNEL FRAMERLIU COMBO - CC/HDLC ARCHITECTURE
REV. P2.0.0
RDY/DTACK
C14
O
READY or DTACK Output:
The exact function of this input pin depends upon which mode the Microproces-
sor Interface has been configured to operate in, as described below.
Intel-Asynchronous Mode - RDY - Ready Output:
If the Microprocessor Interface has been configured to operate in the Intel-Asyn-
chronous Mode, then this output pin will function as the "active-low" READY out-
put.
During a READ or WRITE cycle, the Microprocessor Interface block will toggle
this output pin to the logic low level, ONLY when it (the Microprocessor Inter-
face) 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 hold-
ing 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.
Motorola-Asynchronous Mode - DTACK - Data Transfer Acknowledge Out-
put
If the Microprocessor Interface has been configured to operate in the Motorola-
Asynchronous Mode, then this output pin will function as the "active-low" DTACK
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 Microprocessor Inter-
face) 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.
Power PC 403 Mode - RDY - Ready Output:
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 the Microprocessor 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 output 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.
RESET
M14
I
Hardware Reset Input:
When this "active-low" signal is asserted, the XRT79L71 will be asynchronously
reset. When this occurs, all outputs will be "tri-stated" and all on-chip registers
will be reset to their "default" values.
Table 3: List and Brief Description of the Microprocessor Interface Pins
PIN NAME
PIN/BALL
NUMBER
TYPE
DESCRIPTION