Decimal to Thermometer Encoder
This article contains Verilog-A model for Decimal to Thermometer encoder. This block can be used for behavioral simulation of the pipelined ADCs, programmable gains/BW etc. This model will automatically select number of outputs based on selected number of input binary bits. Usage:
- Create a new cell in Library Manager named dec2therm and select cell type Verilog A;
- Copy and paste the code provided;
- Specify therm_bits variable to be the desired thermometer bits number;
- Specify Start_Bit to be 0 if you want thermometer code to start from 0 or 1 if you want thermometer code to start from 1;
- Perform Check and Save;
- A cell symbol will be created;
- Instantiate dec2term cell into your design;
- Perform Check and Save and run the simulation.
Example: therm_bits = 4, Start_Bit = 0
| Decimal input | Thermometer code |
|---|---|
| 0 | 0000 |
| 1 | 0001 |
| 2 | 0010 |
| 3 | 0100 |
Example: therm_bits = 4, Start_Bit = 1
| Decimal input | Thermometer code |
|---|---|
| 0 | 0001 |
| 1 | 0010 |
| 2 | 0100 |
| 2 | 1000 |
Cell name: dec2term
Model type: Verilog-A
1// Decimal to Thermometer decoder
2// Implements two options:
3// Start_Bit = 0: Decimal 0 equals thermometer 0
4// Start_Bit = 1: Decimal 0 equals thermometer 1
5// Change therm_bits variable for your needs!
6// Author: A. Sidun
7// Source: AnalogHub.ie
8
9`include "constants.vams"
10`include "disciplines.vams"
11`define therm_bits 10 // define number of output bits here
12
13module dec2therm(out);
14
15output [`therm_bits-1:0] out;
16voltage [`therm_bits-1:0] out;
17
18parameter real vdd = 5; // voltage level of logic 1 (V)
19parameter real vss = 0; // voltage level of logic 0 (V)
20parameter integer Decimal_Code = 5; // input decimal code
21parameter integer Start_Bit = 0; // defines if thermometer starts from 0 or 1
22
23real dout[`therm_bits-1:0]; // internal result variable
24genvar i;
25
26analog begin
27
28case (Start_Bit)
29 0: begin // Decimal 0 equals thermometer 0
30 for(i=1;i<`therm_bits+1;i=i+1) begin
31 if(Decimal_Code!=i) begin
32 dout[i-1]=vss;
33 end
34 else begin
35 dout[i-1]=vdd;
36 end
37 end
38 end
39
40 1: begin // Decimal 0 equals thermometer 1
41 for(i=0;i<`therm_bits;i=i+1) begin
42 if(Decimal_Code!=i) begin
43 dout[i]=vss;
44 end
45 else begin
46 dout[i]=vdd;
47 end
48 end
49 end
50endcase
51
52// Plotting outputs
53for (i=0; i<`therm_bits; i=i+1)
54 V(out[i]) <+ transition(dout[i],0,0);
55end
56
57endmodule