Then when we shift it, it will automatically be in BCD form. If it is greather than or equal to five, then we can add three to that number (instead of adding 6 to the shifted number). Knowing that we will convert the number to BCD, we can check the original number before shifting it. If we then want to convert this number to a BCD, we will have to add six to it. If we have the number 0101 (5 decimal), and we shift it left, we know the result will be 1010 (10 decimal), assuming we shift in a zero. A left shift has the same function as multiplying the binary number by two. Recall that a left shift moves all bit values one position to the left (toward the MSB). For example, the binary number 1100 represent the decimal number 12, to convert this 4-bit binary number to its BCD representation, we first note that it is greater than 1001 (9 decimal), so we have to add 0110 (6 decimal), the result is 10010 which is equivalent to 0001 0010 the BCD representation of 12.Ī similar computation could be done using shifts. When converting a binary number to its BCD reperesentation, more than one BCD digit locations might be required. In this lab you will build a circuit that takes an 8-bit binary number and converts it to its 3 digits BCD representation. displaying the result on a seven-segment or LCD display). Many arithmetic operations are done in binary, then converted to BCD for display purposes (i.e. Table 2: Multidigit Decimal Number in BCD The same concept can be applied to decimal numbers with more digits. Table 2 shows an example of using BCD to represent a 3 digits decimal number. Table 1: BCD Representation Decimal Digitĭecimal numbers with multiple digits require 4-bit BCD numbers for each of the digits. Table 1 shows how to represent all decimal digits using BCD, the table also indicate the other six binary numbers (i.e.

Each BCD digit is composed of 4 bits and can represent a number from 0 to 9. Part 1 (Building a Binary-to-BCD Converter)īinary Coded Decimal (BCD) is a numbering system used to represent decimal numbers using binary representations. You will only utilize combinational circuit components, verify the functionality of the converter using a testbench, and test the converter on the FPGA board by using it to display the output of a simple calculator.

The purpose of this lab is to build a Binary-to-BCD converter using the double dabble algorithm (aka the shift-add-3 algorithm).

Verilog decimal to binary conversion