1. Shift Registers
Lecture L8.6
Section 8.3

2. 4-Bit Shift Register

3. shift4.abl MODULE shift4 TITLE '4-bit Shift Register' DECLARATIONS
DECLARATIONS
" INPUT PINS "
CLK PIN 70; " push-button switch (clock)
clear PIN 11; " Switch S6:1
data_in PIN 1; " Switch S7:4
" OUTPUT PINS "
Q3..Q0 PIN 40,41,43,44 ISTYPE 'reg buffer'; " LED
Q = [Q3..Q0]; " 4-bit output vector

4. shift4.abl (cont’d) EQUATIONS Q.AR = clear; Q.C = CLK; Q3.D = data_in;
Q.AR = clear;
Q.C = CLK;
Q3.D = data_in;
Q2.D = Q3;
Q1.D = Q2;
Q0.D = Q1;

5. shift4.abl (cont’d) @radix 16;
@radix 16;
test_vectors([CLK, clear, data_in] -> Q)
[.C.,1,0] -> 0;
[.C.,0,1] -> 8;
[.C.,0,0] -> 4;
[.C.,0,0] -> 2;
[.C.,0,0] -> 1;
[.C.,0,0] -> 0;
[.C.,0,1] -> 0A;
[.C.,0,0] -> 5;
END

6. shift4 simulation

7. Ring Counter

8. ring4.abl MODULE ring4 TITLE '4-bit Ring Counter' DECLARATIONS
DECLARATIONS
" INPUT PINS "
CLK PIN 70; " push-button switch (clock)
start PIN 11; " Switch S6:1
" OUTPUT PINS "
Q3..Q0 PIN 40,41,43,44 ISTYPE 'reg buffer'; " LED
Q = [Q3..Q0]; " 4-bit output vector
Q31 = [Q3..Q1]; " upper 3 bits

9. ring4.abl (cont’d) start = 1 0 0 0 1 EQUATIONS
Q31.AR = start; " asynchronous reset
Q0.AP = start; " asynchronous preset
Q.C = CLK;
Q3.D = Q0;
Q2.D = Q3;
Q1.D = Q2;
Q0.D = Q1;
start = 1

10. ring4.abl (cont’d) @radix 16; test_vectors([CLK, start] -> Q)
@radix 16;
test_vectors([CLK, start] -> Q)
[.C.,1] -> 1;
[.C.,0] -> 8;
[.C.,0] -> 4;
[.C.,0] -> 2;
[.C.,0] -> 1;
END

11. ring4 simulation

12. Ring Counter

13. Johnson Counter

14. Exercise Detect input sequence 1101
din
fsm
clk
dout
clr
din
dout

15. Use Shift Register dout 1 1 1 din Q3 Q2 Q1 Q0 CLK D Q D Q D Q D Q CLK1 1
din Q3 Q2 Q1 Q0 D Q D Q D Q D Q
CLK !Q
CLK !Q
CLK !Q
CLK !Q
CLK

16. A Random Number Generator

17. Q3 Q2 Q1 Q0 C E F B
Q3 Q2 Q1 Q0 A D