XRT72L56 Datasheet, PDF (68/486 Pages) Exar Corporation – SIX CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER

XRT72L56 SIX CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
REV. P1.1.2
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PRELIMINARY
TABLE 2: DESCRIPTION OF THE MICROPROCESSOR INTERFACE SIGNALS THAT EXHIBIT CONSTANT ROLES IN BOTH
THE INTEL AND MOTOROLA MODES
PIN NAME TYPE
DESCRIPTION
MOTO
I
Selection input for Intel/Motorola µP Interface.
Setting this pin to a logic "High" configures the Microprocessor Interface to operate in the Motorola
mode. Likewise, setting this pin to a logic "Low" configures the Microprocessor Interface to operate
in the Intel Mode.
D[7:0]
I/O Bi-Directional Data Bus for register read or write operations
A[11:0]
I
Twelve Bit Address Bus input:
This Twelve bit Address Bus is provided to allow the user to select an on-chip register or on-chip
RAM location and Select the desired Framer Channel to address.
CS
I
Chip Select input.
This active-”Low” signal selects the Microprocessor Interface of the UNI device and enables read/
write operations with the on-chip registers/on-chip RAM.
INT
O Interrupt Request Output:
This open-drain/active-low output signal will inform the local µP that the UNI has an interrupt condi-
tion that needs servicing.
TABLE 3: PIN DESCRIPTION OF MICROPROCESSOR INTERFACE SIGNALS - WHILE THE MICROPROCESSOR INTERFACE
IS OPERATING IN THE INTEL MODE
PIN NAME
EQUIVALENT PIN
IN INTEL
ENVIRONMENT
TYPE
DESCRIPTION
ALE_AS
ALE
I Address-Latch Enable: This “active-high” signal is used to latch the contents on
the address bus, A[11:0]. The contents of the Address Bus are latched into the
A[11:0] inputs on the falling edge of ALE_AS. Additionally, this signal can be
used to indicate the start of a burst cycle.
RD_DS
RD*
I Read Signal: This “active-low” input functions as the read signal from the local
µP. When this signal goes "Low", the UNI Microprocessor Interface will place the
contents of the addressed register on the Data Bus pins (D[15:0]). The Data Bus
will be "tri-stated" once this input signal returns "High".
WR_R/W
WR*
I Write Signal: This "active-low" input functions as the write signal from the local
µP. The contents of the Data Bus (D[15:0]) will be written into the addressed reg-
ister (via A[11:0]), on the rising edge of this signal.
RDY_DTCK READY*
O Ready Output: This "active-low" signal is provided by the UNI device, and indi-
cates that the current read or write cycle is to be extended until this signal is
asserted. The local µP will typically insert WAIT states until this signal is
asserted. This output will toggle "Low" when the device is ready for the next
Read or Write cycle.
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