XRT79L71 Datasheet, PDF (17/441 Pages) Exar Corporation – 1 - CHANNEL DS3/E3 ATM UNI/PPP COMBO IC

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PRELIMINARY
1 - CHANNEL DS3/E3 ATM UNI/PPP COMBO IC
XRT79L71
REV. P1.0.3
PIN DESCRIPTIONS
PIN #
NAME
TYPE
DESCRIPTION
C14
RDY/DTACK O READY or DTACK:
This active-low output pin will function as the READY output when the Microproces-
sor Interface is configured to operate in the Intel Mode; and will function as the
DTACK output, when the Microprocessor Interface is running in the Motorola Mode.
Intel Mode - READY output:
When the Framer/UNI negates this output pin (e.g., toggles it "Low") it indicates to
the Microprocessor that the current READ or WRITE operation is to be extended until
this signal is asserted (e.g., toggled "High").
Motorola Mode - DTACK Data Transfer Acknowledge Output:
The Framer/UNI will assert this pin in order to inform the Microprocessor that the
present READ or WRITE cycle is nearly complete. If the Framer/UNI requires that
the current READ or WRITE cycle be extended, then the Framer/UNI will delay its
assertion of this signal. The 68000 family of Microprocessors requires this signal
from its peripheral devices, in order to quickly and properly complete a READ or
WRITE cycle.
M14
RESET
I Reset Input:
When this active-low signal is asserted, the Framer/UNI device will be asynchro-
nously reset. When this occurs, all outputs will be tri-stated and all on-chip registers
will be reset to their default values.
H16
µPCLK
I Microprocessor Interface Clock Input:
This clock input signal is used for synchronous/burst/DMA data transfer operations.
This clock can be running up to 33MHz.
B16
WR/R/W
I Write Strobe Intel Mode:
If the Microprocessor Interface is configured to operate in the Intel Mode, then this
active-low input pin functions as the WR (WRITE Strobe) input signal from the Micro-
processor. Once this active-low signal is asserted, the Framer/UNI will latch the con-
tents of the bi-directional data (D[7:0]) into the addressed registers or Buffer location
within the Framer/UNI IC.
R/W Input Pin Motorola Mode:
When the Microprocessor Interface Section is operating in the Motorola Mode, then
this pin is functionally equivalent to the R/W pin. In the Motorola Mode, a READ
operation occurs if this pin is at a logic "1". Similarly a WRITE operation occurs if this
pin is at a logic "0".
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