The view of data as flowing through a design, from input to output. A dataflow model specifies the functionality of the entity without explicitly specifying its structure. This functionality shows the flow of information through the entity, which is expressed pri¬marily using concurrent signal assignment statements and block statements. VHDL code is inherently concurrent (parallel). Concurrent code is also called dataflow code.
architecture DATAFLOW of NAND2 is begin X <= a nand b; end DATAFLOW;
In above NAND gate code is described using single concurrent signal assignment statement. A signal assignment is identified by the symbol “ <=”.
architecture Dataflow of Decoder is begin led(3) <= bcd(0) and bcd(1); led(2) <= bcd(0) and (not bcd(1)); led(1) <= (not bcd(0)) and bcd(1); led(0) <= (not bcd(0)) and (not bcd(1)); end Dataflow;
All the four statements here are executed concurrently and each of them is activated individually when any of its input signals changes its value.
architecture dataflow of Half-adder is begin sum <= A XOR B; carry <= A AND B; end dataflow;