; default: ;--fromenv (comma-separated list of flags to set from the environment [use'export FLAGS_flag1=value']); default: ;--tryfromenv (comma-separated list of flags to try to set from theenvironment if present); default: ;--undefok (comma-separated list of flag names that it i...
If multiple statements need to be placed inside the if or else part, it needs to be enclosed within begin and end. if ([expression]) Single statement // Use "begin" and "end" blocks for more than 1 statements if ([expression]) begin Multiple statements end // Use else to execute sta...
25 Error: VHDL error at shift_reg.vhd(24): can't synthesize logic for statement with conditions that test for the edges of multiple clocks ---同一进程中含有两个或多个if(edge)条件,(一个进程中之能有一个时钟沿) 26 Error: Can't resolve multiple constant drivers for net "datain_reg[22]...
25 Error: VHDL error at shift_reg.vhd(24): can't synthesize logic for statement with conditions that test for the edges of multiple clocks ---同一进程中含有两个或多个if(edge)条件,(一个进程中之能有一个时钟沿) 26 Error: Can't resolve multiple constant drivers for net "datain_reg[22]...
A variant of the D-flop is one with an asynchronous reset; there is a convention that the reset state will be the first if clause within the statement. regq;always@(posedgeclkorposedgereset)if(reset)q<=0;elseq<=d; The next variant is including both an asynchronous reset and asynchronous...
conditions in the status table. If, in actual use, encounter a situation that is not defined in the status table, an uncertain value x is output. Using custom primitives is intuitive, but if there are many input variables, the state table becomes very complicated. In many cases, user-...
Instead of using multiple nested if-else statements, one for each value we're looking for, we use a single case statement: this is similar to switch statements in languages like C++. Case statements begin with the reserved word case and end with the reserved word endcase (Verilog does not...
25 Error: VHDL error at shift_reg.vhd(24): can't synthesize logic for statement with conditions that test for the edges of multiple clocks ---同一进程中含有两个或多个if(edge)条件,(一个进程中之能有一个时钟沿) 26 Error: Can't resolve multiple constant drivers for net "datain_reg[22]...
high and low levels of abstraction. Designing hardware with a language like Verilog allows usage of software concepts such as parallel processing and object-oriented programming. Verilog has a syntax similar to C and Pascal, and is supported by XST as IEEE 1364. The Verilog support in XST pro...
The case statement checks if the given expression matches one of the other expressions in the list and branches accordingly. It is typically used to implement a multiplexer. The if-else construct may not be suitable if there are many conditions to be che