![]() We use the net types to model connections in our digital circuits. We use these two different groups to model different elements of our digital circuits. The code snippet below shows the general syntax for representing digital data in verilog.īroadly speaking, the basic data types in verilog can be split into two main groups - net types and variable types. Therefore, we can create data busses which contain as many bits as we choose. This is because we are fundamentally describing hardware circuits when we use verilog. Unlike in other programming languages, we also need to define the number of bits we have in our data representation. We can express this data as either a binary, hexadecimal or octal value. When we write verilog, we often need to represent digital data values in our code. As a result, there is often no need necessary to explicitly perform type conversions in verilog. When we assign data to a signal in verilog, the data is implicitly converted to the correct type in most cases. We can also use types which interpret our data as if it were a numeric value. We can use types which interpret data purely as logical values, for example. ![]() The type which we specify is used to define the characteristics of our data. This includes a discussion of data respresentation, net types, variables types, vectors types and arrays.Īlthough verilog is considered to be a loosely typed language, we must still declare a data type for every port or signal in our verilog design. This could be remedied by instead implementing a positive edge detection circuit for the start button input signal.In this post, we talk about the most commonly used data types in Verilog. 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. 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. 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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