An algorithmic state machine, or ASM, chart groups a state's actions with decision boxes and conditional-output boxes. It describes clocked control flow while retaining hardware timing meaning. A path through one state block determines actions and the next state for that cycle.
Worked example
A controller in WAIT checks request in a decision box. If request is zero, it returns to WAIT. If request is one, it asserts a conditional accept signal and chooses RUN as the next state. A state output busy can be asserted in the RUN state box.
What to watch for
An ASM chart is not a general software flowchart. Decisions within a state block do not necessarily consume separate clock cycles; state transitions establish the cycle boundaries.
Try it yourself
Does passing through two decision boxes in one ASM state automatically take two cycles?
Answer: No. Both can describe combinational decisions within the same state interval, subject to the resulting timing path.
How to study this topic
Begin with named states and a complete transition table. Then choose encodings and derive the logic. Trace inputs over several cycles, checking outputs as well as next states, including reset and unexpected encodings.
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