
Dueck R.Digital design with CPLD applications and VHDL.2000
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Answers to Selected Odd-Numbered Problems |
789 |
FIGURE ANS5.19B
FIGURE ANS5.21


Answers to Selected Odd-Numbered Problems |
791 |
ARCHITECTURE mux8 OF quad8to1 IS
BEGIN
—— Selected Signal Assignment
MUX4: WITH s SELECT |
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y <= |
d0 WHEN 0, |
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d1 |
WHEN 1, |
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d2 |
WHEN 2, |
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d3 |
WHEN 3, |
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d4 |
WHEN 4, |
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d5 |
WHEN 5, |
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d6 |
WHEN 6, |
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d7 |
WHEN 7; |
END mux8; |
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FIGURE ANS5.27
The simulation of this circuit is shown in Figure ANS5.27.
5.29—— oct4to1.vhd
——Four-channel 8-bit multiplexer
——One of four sets eight inputs
——(d07..d00), (d17..d10), (d27..d20), or (d37..d30)
——is directed to a an output (y), based on the status of two
——select inputs (s1, s0).
ENTITY oct4to1 IS
PORT(
s |
: IN |
INTEGER RANGE 0 to 3; |
d0 |
: IN |
BIT_VECTOR (7 downto 0); |
d1 |
: IN |
BIT_VECTOR (7 downto 0); |
d2 |
: IN |
BIT_VECTOR (7 downto 0); |
d3 |
: IN |
BIT_VECTOR (7 downto 0); |
y |
: OUT BIT_VECTOR (7 downto 0)); |

792 Answers to Selected Odd-Numbered Problems
END oct4to1;
ARCHITECTURE mux4 OF oct4to1 IS
BEGIN
—— Selected Signal Assignment
MUX8: WITH s SELECT |
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y |
<= |
d0 WHEN 0, |
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d1 |
WHEN 1, |
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d2 |
WHEN 2, |
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d3 |
WHEN 3; |
END mux4; |
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FIGURE ANS5.29
The simulation is shown in Figure ANS5.29.
5.31ENTITY mux_8ch IS
PORT( |
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sel |
: IN |
BIT_VECTOR (2 downto 0); |
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d |
: IN |
BIT_VECTOR (7 downto 0); |
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y |
: OUT BIT); |
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END mux_8ch; |
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ARCHITECTURE a OF mux_8ch IS |
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BEGIN |
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—— Selected Signal Assignment |
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MUX8: WITH sel SELECT |
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y |
<= |
d(0) WHEN “000”, |
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d(1) |
WHEN “001”, |
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d(2) |
WHEN “010”, |
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d(3) |
WHEN “011”, |
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d(4) |
WHEN “100”, |
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d(5) |
WHEN “101”, |
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d(6) |
WHEN “110”, |
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d(7) |
WHEN |
An 8-to-1 MUX can be easily extended to a 16-bit device |
“111”; |
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by adding one select input, eight data inputs, and eight |
END a; |
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