This could be remedied by instead implementing a positive edge detection circuit for the start button input signal. The intermediate state showing “88” occurs only when the button is pressed and the master FSM rapidly cycles through its states, until it is disengaged. For instance: You can however always use the decimal (hexadecimal,octal) number format to enter values in verilog. You can however always use the decimal (hexadecimal,octal) number format to enter values in verilog. We can see that unlike before where the result was always routed to the output display, we now have to enable the start line to compute the conversion. A bitwise operator works in bit by bit fashion, therefore its binary by definition. state register always posedge clk, posedge reset)ī2b_start = 1'b1 // assert start line to bcd2bin circuitĮnd b2b: if (b2b_done_tick) // once bcd2bin conversion done, go back to idle bin(bin)) ĭisplayMuxBasys disp_unit (.clk(clk). For the conversion of BCD 42, 4 is multiplied by 10, and 2 is added to it, giving us 101010, which is the binary representation of 42.īcd2bin_direct bcd2bin_direct_unit (.bcd1(bcd). The first algorithm will simply take the “tens” BCD digit, multiply it by 10, and add the “ones” digit to it. We will therefore concern ourselves with designing a circuit to convert a 2 digit BCD number to a 7 bit binary representation (2 7 = 128 > 99, the largest 2 digit BCD number we can input). We can use the 8 input switches to encode 2 BCD numbers of 4 bits each. We will be designing for the Basys 2 FPGA board which has 8 input switches. We will consider two algorithms to perform the conversion, the first being a direct arithmetic approach, and the second an iterative algorithm using a finite state machine with data path (FSMD). I chose to detail this direction of conversion as binary to BCD conversion circuits are easily be found by a quick web search. We will focus on designing a conversion circuit that converts a BCD formatted number to to a binary formatted number. The BCD format is common in electronic systems where numeric digits are displayed, as well as in systems where the rounding and conversion errors introduced by binary floating point representation and arithmetic are undesirable. For example, 42 is represented in BCD format by the binary representations of 4 and 2, as shown above. Binary Coded Decimal format is a binary encoding of decimal numbers that represents each decimal digit by a fixed binary number.
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