Casting is applicable to value, variable or to an expression.Static casting will be checked during compilation, so there won’t be run-time checking and error reporting.As the name says ‘Static’, the conversion data type is fixed.Static casting converts one data type to another compatible data types (example string to int).SystemVerilog static casting is not applicable to OOP.In systemVerilog, there are two types of casting, The method of data type conversion is called casting. Otherwise, the assignment of different data type results in a compilation error. Some situations need assignment of different data type, in such situations, it is necessary to convert data type and assign. During value or variable assignment to a variable, it is required to assign value or variable of the same data type. Similarly, SystemVerilog casting means the conversion of one data type to another datatype. In Manufacturing, Casting is a process in which liquid metal is converted into the desired object. assigning parent class handle to child class handle.assigning child class handle to parent class handle.Once built, program the board and verify its function. You will need to make appropriate edits in build.tcl and unsigned_arithmetic.xdc. Once your module is verified, implement it with these port mappings:Īlso don’t forget the clock. You will need to choose appropriate test patterns and an algorithm to generate them. Verify the Counter in SimulationĮdit the testbench to test overflow cases, and verify that your module never overflows on up or dn events. If an overflow would occur, then q should not be changed. The logic above seems simple enough, but you need to modify this logic so that it detects overflow. The logic should look something like this:Īlways posedge clk) begin if (rst) q <= a else begin if (up) q <= q + b else if (dn) q <= q - b end end dn causes the counter to decrement by b.up causes the counter to increment by b. Make a module called up_down_counter with behavior specified as follows: How can the multiplier detect overflow? See if you can come up with a solution (Hint: consider the most significant non-zero digit in each of the inputs). Given two 8-bit inputs, a multiplier produces an 8-bit output. This is a problem for algorithms that perform repeated multiplications, since the bit-width must grow geometrically with each operation.Ī common computing scenario uses the same bit-width for all integers, let’s say 8 bits. To multiply two 4-bit numbers, the largest product is 15x15=225=8’b11100001, an eight-bit number.Īs the input width grows, generally the output width needs to be the sum of the input widths. The largest product is 7x7=49=6’b100001, a six-bit number. These options are fairly straightforward when dealing with addition or subtraction: you either increase the output width by 1 bit, or capture the last carry-out as an overflow indicator. Detect overflow and provide a separate overflow error output.Give the output vector a larger width than the inputs. To avoid overflow problems, there are two approaches: When 11 is incremented, it overflows and rolls back to zero. This could be made even simpler by using an addition statement:Īt each clock cycle, the 2-bit value increments by 1, so the pattern is 00 We later simplified the statements to two assignments, en <= d d <= ~en. The operation table below shows a-b, with the rows indicating a and the columns as b: -Īs a simple useful application, recall the testbench from our first assignment, where if/then statements were used to cycle through all cases of. Sometimes it creates a hazard for safety or security.Ī similar thing happens with subtraction. Note that whenever the sum is “too big”, the numbers “roll over” to zero. For this module, the operation table is + The inputs and output are all 3-bit values. This module uses a blocking assignment to implement a combinational (non- clocked) sum. Module simple_adder ( input a, input b, output q ) always begin q = a + b end endmodule
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