
MOTOROLA
Chapter 8. Signal Descriptions
8-5
Signal Configurations
8.2.2.1
Unidirectional/Bidirectional Signals
Table 8-2 illustrates the conditions for setting up uni- or bidirectional signals external to the
core, showing how the high-impedance control signal should be tied.
8.2.2.2
Logic Gate Equivalent and Bidirectional Signals
All bidirectional signals from the 60x bus interface are implemented as separate input,
output, output enable, and high-impedance enable signals, and in some cases, there is an
input enable signal. Figure 8-2 shows an example of how these signals can be used to create
a bidirectional signal outside of the core.
Figure 8-2. Logic Diagram for Bidirectional Signals
Table 8-3 represents the following conditions for a bidirectional signal created by
wire-ORing the input and output signals from the core:
If core_xxx_tre = 1, the core_xxx_oe signal controls the output on the address or
data bus.
If core_xxx_tre = 0, the data is driven on the bidirectional signal.
Table 8-2. Conditions for Unidirectional/Bidirectional Signals
Signal Type
core_xxx_tre
(Input Signal)
core_xxx_oe
(Output Signal)
core_xxx_ien
(Output Signal)
core_xxx_in,
core_xxx_out
Unidirectional
Negated
(tie low)
Output enable signal is
used when valid data is
presented to the system
level logic.
Input enable signal is used
when valid data is required
to be presented to the
internal core logic.
Used as unidirectional
signals to or from the
system level logic
interface.
Bidirectional
Asserted
(tie high)
Typically not used or if it is
used, it has similar
conditions as for a
unidirectional signal.
Typically not used or if it is
used, it has similar
conditions as for a
unidirectional signal.
Input and output signals
are wire-ORed together to
generate bidirectional
signal with value of high,
low, or high-impedance
appropriately.
core_xxx_tre
Address/Data Bus/Control
(Bidirectional)
N
core_xxx_oe
Data Out
Data In
F
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n
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