registers and counters - university of british columbiacourses.ece.ubc.ca/256/lectures/2010/digital...
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Registers and Counters
Chapter 6
Steve Oldridge
Dr. Sidney Fels
Topics
• Registers
• Shift Registers
• Ripple Counters
• Synchronous Counters
• Other Counters
• HDL
Registers & Counters Overview
• Register
– Group of flip-flops
– n-bits (1 per flip-flop)
– n-bits of binary
• Counter
– Register with a fixed function
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4-bit register
Parallel Load
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Shift Registers
Serial Transfer
Serial Transfer Example
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Serial Adder
State Table
Serial Adder Circuit
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Universal Shift Register
• Clear
• Clock
• Shift Right
• Shift Left
• Parallel load
• n Parallel Outputs
• Control
Universal Shift Register
Shift Register Controls
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Ripple Counters
Ripple Counter Timing Diagram
Close Up
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Counting Sequences
State Diagram of BCD counter
BCD Ripple Counter
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Three decade counter
Synchronous Counters
Binary Up Down Counter
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BCD Synchronous Counter State Table
4-bit Binary Counter
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Function of the Counter
BCD Counter
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Other types of Counters
Counter with unused states
Ring Counter
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Ring Counter
Johnson Counter
Johnson Counter
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HDL Binary Counter
module Binary_Counter_4_Par_Load (
output reg [3:0] A_count, // Data output
output C_out, // Output carryinput [3:0] Data_in, // Data input input Count, // Active high to count
Load, // Active high to loadCLK, // Positive edge sensitive
Clear // Active low);
assign C_out = Count & (~Load) & (A_count == 4'b1111);always @ (posedge CLK, negedge Clear)
if (~Clear) A_count <= 4'b0000;else if (Load) A_count <= 4'b0000;
else if (Count) A_count <= A_count + 1'b1;else A_count <= A_count; // redundant statement
endmodule
Registers & Counters Review
• Register– Group of flip-flops
– D, J/K,T
• Counter– Register with a fixed function
– Ripple Counter
– Parallel Load
– Ring Counter
– Johnson Counter