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Design Units
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Types & Objects
std_logic std_logic_vector unsigned signed integer boolean signal variable constant array type
Concurrent Logic
concurrent assignment conditional signal assignment selected signal assignment with select component instantiation entity instantiation generate for generate if block statement alias
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Sequential Statements
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FSM & RTL
state enum next-state logic Moore output Mealy output reset synchronous reset asynchronous clock enable counter shift register register file
Verification
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VHDL / Processes

falling_edge

Learn falling_edge in VHDL through a focused explanation, a dedicated construct-specific example, an engineering boundary, and a mastery check.

10 min read • Intermediate

falling_edge is an atomic VHDL topic inside Processes. This lesson focuses on how the falling_edge construct is written, what it changes, and when it is the right tool.

Trace the example line by line. Identify the exact syntax for falling_edge, the input state before it runs, and the resulting value, control flow, database state, hardware behavior, or runtime effect afterward. Neighboring lessons use different constructs rather than renamed copies of this one.

Topic-specific example

vhdl-04-04-falling-edge.vhd
vhdl Try It Live 
process(clk)
begin
  if falling_edge(clk) then q <= d; end if;
end process;
Edge case / engineering note

For falling_edge, test the boundary that belongs to this exact feature rather than a generic failure case. Check invalid or empty input, NULL/unknown state, numeric limits, transaction or exception behavior, synthesis/runtime constraints, ownership/permission rules, or backtracking/control-flow effects where they apply.

Content source & attribution
Original Syntaxis Content · Original Syntaxis Content

Lesson quizzes

falling_edge Mastery Check →
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clocked process