
x r
PRELIMINAZRY
E3 UNI FOR ATM
XRT7234
REV. P1.0.0
39
The local
μ
configures the UNI (into a desired operating mode) by writing data into specific addressable on-chip
“Read/Write” registers; or on-chip RAM. The microprocessor interface provides the signals which are required for a
general purpose microprocessor to read or write data into these registers. The Microprocessor Interface also supports
“polled” and interrupt-driven environments. These interface signals are described below in Tables 1, 2, and 3. The micro-
processor interface can be configured to operate in the “Motorola” mode or in the “Intel” mode. When the Microprocessor
Interface is operating in the “Motorola” mode, then some of the control signals function in a manner as required by the
Motorola 68000 family of microprocessors. Likewise, when the Microprocessor Interface is operating in the “Intel”
Mode, then some of these control signals function in a manner as required by the Intel 80xx family of microprocessors.
Tables 1 lists and describes those Microprocessor Interface signals whose role is constant across the two modes.
Table 2 describes the role of some of these signals when the Microprocessor Interface is operating in the “Intel”
Mode. Likewise, Table 3 describes the role of these signals when the Microprocessor Interface is operating in the
“Motorola” Mode.
Table 1. 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
μ
P 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 “l(fā)ow” configures the Microprocessor Interface to operate in
the “Intel” Mode.
Width16
I
Select input for the Data Bus width: Setting this pin to a logic “high” configures the width of the Micro-
processor Interface data bus width to be 16 bits. Likewise, setting this pin to a logic “l(fā)ow” selects a
data bus width of 8 bits.
D[15:0]
I/O
Bi-directional Data Bus for register read or write operations.
Note: If the “Width16” input is “l(fā)ow”, then only D[7:0] is active.
A[8:0]
I
Nine Bit Address Bus input: This nine bit Address Bus is provided to allow the user to select an on-chip
register or on-chip RAM location.
CSB*
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.
IntB*
O
Interrupt Request Output: This “open-drain/active-low” output signal will inform the local
μ
P that the
UNI has an interrupt condition that needs servicing.