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A/D Converter Control

A/D Converter Control. Discussion D8.6. Analog-to-Digital Converters. Converts analog signals to digital signals 8-bit: 0 – 255 10-bit: 0 – 1023 12-bit: 0 – 4095 Successive Approximation. Method of Successive Approximation. Implementing Successive Approximation.

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A/D Converter Control

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  1. A/D ConverterControl Discussion D8.6

  2. Analog-to-Digital Converters • Converts analog signals to digital signals • 8-bit: 0 – 255 • 10-bit: 0 – 1023 • 12-bit: 0 – 4095 • Successive Approximation

  3. Method of Successive Approximation

  4. Implementing Successive Approximation

  5. Implementing Successive Approximation

  6. A/D CPLD Control

  7. Use Mealy Machine Inputs to C1: adstart, gt, done Outputs from C2: sarald, sh, adld, msel

  8. A/D Control Unit

  9. A Mealy state machine

  10. ADctl adflg = done; msel = ~gt; adld = done; sarld = ~done; sh = ~done;

  11. A Mealy state machine Use one-hot encoding: one flip-flop per state

  12. module DFF (D, clk, clr, Q); input clk, clr ; wire clk, clr ; input D ; wire D ; output Q ; reg Q ; always @(posedge clk orposedge clr) if(clr == 1) Q <= 0; else Q <= D; endmodule

  13. module DFF1 (D, clk, reset, Q); input clk, reset; wire clk, reset ; input D ; wire D ; output Q ; reg Q ; always @(posedge clk orposedge reset) if(reset == 1) Q <= 1; else Q <= D; endmodule

  14. // adconv control module ADctrl(Clk, Clear, gt, adstart, done, msel, sarld, sh, adld, adflg); input Clk, Clear, gt, adstart, done; output msel, sarld, sh, adld, adflg; wire msel, sarld, sh, adld, adflg; wire start, keep, remove; wire startD, keepD, removeD; assign startD = start & ~adstart | keep & done | remove & done; assign keepD = start & adstart & gt | keep & gt & ~done | remove & gt & ~done; assign removeD = start & adstart & ~gt | keep & ~gt & ~done | remove & ~gt & ~done;

  15. DFF1 startFF(.D(startD), .clk(Clk), .reset(Clear), .Q(start)); DFF keepFF(.D(keepD), .clk(Clk), .clr(Clear), .Q(keep)); DFF removeFF(.D(removeD), .clk(Clk), .clr(Clear), .Q(remove));

  16. // C2 Outputs assign adflg = done; assign msel = ~gt; assign adld = done; assign sarld = ~done & keep | ~done & remove | adgo & start; assign sh = ~done & keep | ~done & remove | adgo & start; endmodule

  17. // Title : A/D converter module adconv(clock, clear, adstart, gt, adflg, sar, adreg); input clock, clear, adstart, gt; output adflg; output [3:0] sar, adreg; wire adflg, msel, sarld, adld, sh, done; wire [3:0] sar, adreg; ADpath adc1(.clk(clock),.reset(clear),.msel(msel),.sh(sh), .sarld(sarld),.adld(adld),.sar(sar),.ADR(adreg), .done(done)); ADctrladc2(.Clk(clock),.Clear(clear),.gt(gt), .adstart(adstart),.done(done),.msel(msel), .sarld(sarld),.sh(sh),.adld(adld), .adflg(adflg)); endmodule

  18. A Mealy state machine Use binary encoding: two flip-flops

  19. // adconv control module ADctrl(Clk, Clear, gt, adstart, zero, msel, sarld, sh, adld, adflg); input Clk, Clear, gt, adstart, zero; output msel, sarld, sh, adld, adflg; reg msel, sarld, sh, adld, adflg; reg[2:0] present_state, next_state; parameter start = 2'b00, keep = 2'b01, remove = 2'b11;

  20. always @(posedge Clk orposedge Clear) begin if (Clear == 1) present_state <= start; else present_state <= next_state; end

  21. always @(present_state or adstart or gt or done) begin case(present_state) start: if(adstart == 1) next_state <= load; elseif(gt == 1) next_state <= keep; else next_state <= remove; keep: if(done == 1) next_state <= start; elseif(gt == 1) next_state <= keep; else next_state <= remove; remove: if(done == 1) next_state <= start; elseif(gt == 1) next_state <= keep; else next_state <= remove; default next_state <= start; endcase end

  22. // C2 Outputs assign adflg = done; assign msel = ~gt; assign adld = done; assign sarld = ~done & keep | ~done & remove | adgo & start; assign sh = ~done & keep | ~done & remove | adgo & start; endmodule

  23. A/D Control Unit

  24. // Title : A/D converter module adconv(clock, clear, adstart, gt, adflg, sar, adreg); input clock, clear, adstart, gt; output adflg; output [3:0] sar, adreg; wire adflg, msel, sarld, adld, sh, done; wire [3:0] sar, adreg; ADpath adc1(.clk(clock),.reset(clear),.msel(msel),.sh(sh), .sarld(sarld),.adld(adld),.sar(sar),.ADR(adreg), .done(done)); ADctrl adc2(.Clk(clock),.Clear(clear),.gt(gt),.adstart(adstart), .done(done),.msel(msel),.sarld(sarld),.sh(sh), .adld(adld), .adflg(adflg)); endmodule

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