Chapter 10 Advanced Features

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Chapter 10 Advanced Features
Dec. 1st
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Generate Statement

• Concurrent statements can be conditionally
  selected or replicated using the generate
  statement
• Using the for-generation scheme, concurrent
  statements can be replicated a predetermined
  number of times.
• With the if-generation scheme, concurrent
  statements can be conditionally elaborated.

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Example revisit4 bit full-adder

b
(3)

a
(3)

b
(0)

a
(0)

b
(1)

a
(1)

b
(2)

a
(2)


X0

X1

Cin
X2

X3

C(0)




C
(1)
C
(2)

(3)


CoutC(4)
C
sum
(3)

sum
sum
sum
(0)

(1)

(2)

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Vhdl code
5
Simulation results
6
Using Generate statement
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Simulation results
8
Another example revisit
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Another example revisit
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Equivalent description using generate statement
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Simulation results
12
Conditional generate statement
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Conditional generate statement
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Simulation results
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Aliases
An alias declares an alternate name for all or
part of a named item. It provides a convenient
shorthand notation for items that have long
names. It also provides a mechanism to refer to
the same named item in different ways depending
on the context.
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Aliases
15
8
5
4
3
0
DATA_BUS
RESET
STATUS
RX_READY
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Attribute
Attributes are a feature of VHDL that allow you
to extract additional information about an object
(such as a signal, variable or type) that may not
be directly related to the value that the object
carries. predefined attributes user-defined
attributes
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Example of attribute
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Value Attributes
Value kind attributes returning values from array
of values 'left 'right 'high 'low 'length
'ascending
'left Returns the index of the left-most element
of an array   Example
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Value Attributes
'right Returns the index of the right-most
element of an array
'high Returns the largest value of the indices
of an array
low, 'length, 'ascending can be found in the
textbook
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Function attributes
Function attributes represent functions that are
called to obtain a value.
Returning information about a given type, signal,
or array value 'pos(value) 'val(value)
'succ(value) 'pred(value) 'leftof(value)
rightof(value)
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Function attributes
'pos(name) Returns an integer number
corresponding to the position of the "name" in a
list
'val(position) Returns the value of the variable
at the specified position in a list of
variables.
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Function attributes
'succ(value) Returns the value of the variable
at the position following the specified item in
a list of variables.
'Pred(value) Returns the value of the variable
at the position preceding the specified item in
a list of variables.
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Function attributes
Function kind attributes returning information
about signals 'event 'active 'last_event
'last_value 'last_active
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Function attributes
'event Returns an value 'true' if the signal
changed in value during the current simulation
delta cycle.
'active Returns an value 'true' if any
transaction (scheduled event) occurred on the
specified signal during the current simulation
delta cycle
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Function attributes
Signal kind attributes 'delayed(time)
'stable(time) 'quiet(time) 'transaction These
attributes create new signals from the signals
with which they are associated. 'delayed(time),
'quiet(time) , 'transaction are not supported by
xilinx webpack.
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Function attributes