XRT79L71 Datasheet, PDF (16/441 Pages) Exar Corporation – 1 - CHANNEL DS3/E3 ATM UNI/PPP COMBO IC

XRT79L71
REV. P1.0.3
PRELIMINARY
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1 - CHANNEL DS3/E3 ATM UNI/PPP COMBO IC
PIN DESCRIPTIONS
PIN #
NAME
TYPE
DESCRIPTION
MICROPROCESSOR INTERFACE
F16
A0
I Address Bus Input pins Microprocessor Interface:
F15
A1
F14
A2
These pins are used to select the on-chip Framer/UNI registers and RAM space for
READ and WRITE Operations with the Microprocessor.
F13
A3
G16
A4
G15
A5
G14
A6
G13
A7
C16
A8
D15
A9
D16
A10
E16
A11
E15
A12
E14
A13
E13
A14
D11
D0
I/O Bi-Directional Data Bus pins Microprocessor Interface:
C12
D1
These pins are used to drive and receive data over the bi-directional data bus.
B13
D2
A14
D3
D12
D4
C13
D5
B14
D6
A15
D7
A16
ALE/AS
I Address Latch Enable/Address Strobe:
This input pin is used to latch the address present at the Microprocessor Interface
Address Bus pins (A[6:0]) into the Framer/UNI Microprocessor Interface block and to
indicate the start of a READ or WRITE cycle. This input pin is active-high, in the Intel
Mode and active low in the Motorola Mode.
D14
CS
I Chip Select Input:
The user must assert this active low signal in order to select the Microprocessor
Interface for READ and WRITE operations between the Microprocessor and the UNI/
Framer on-chip registers and RAM locations.
D13
INT
O Interrupt Request Output:
This open-drain, active-low output signal will be asserted when the Framer/UNI
device is requesting interrupt service from the Microprocessor. This output pin
should typically be connected to the Interrupt Request input of the Microprocessor.
C15
RD/DS/
I READ Strobe Intel Mode:
If the Microprocessor Interface is operating in the Intel Mode, then this input pin will
function as the RD (READ Strobe) input signal from the Microprocessor. Once this
active-low signal is asserted, then the Framer/UNI will place the contents of the
addressed register within the Framer/UNI IC on the Microprocessor Bi-directional
Data Bus (D[7:0]). When this signal is negated, the Data Bus will be tri-stated.
Data Strobe Motorola Mode:
If the Microprocessor Interface is operating in the Motorola Mode, then this input will
function as the DS (Data Strobe) signal.
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