added UML

UML/activity.plantuml

@@ -0,0 +1,51 @@
+@startuml
+start
+
+:posedge clk;
+
+'--- Step timer ---
+if (step_cnt >= (freq_idx == 1 ? STEP_2SEC_MAX : STEP_4SEC_MAX)) then (yes)
+  :step_cnt := 0;
+  if (freq_idx == 5) then (yes)
+    :freq_idx := 0;
+  else (no)
+    :freq_idx := freq_idx + 1;
+  endif
+else (no)
+  :step_cnt := step_cnt + 1;
+endif
+
+'--- Recalculate half-period ---
+:max_count := calc_max_count(freq_idx);
+
+'--- Blink generation for led ---
+if (max_count == 0) then (0 Hz)
+  :blink_cnt := 0;
+  note right
+    led_base сохраняет предыдущее
+    значение (нет мигания)
+  end note
+else (f > 0)
+  if (blink_cnt >= max_count) then (toggle)
+    :blink_cnt := 0;
+    :led_base := ~led_base;
+  else (count)
+    :blink_cnt := blink_cnt + 1;
+  endif
+endif
+
+'--- 1 Hz generation for pin ---
+if (pin_cnt >= PIN_1HZ_HALF_MAX) then (toggle)
+  :pin_cnt := 0;
+  :pin_base := ~pin_base;
+else (count)
+  :pin_cnt := pin_cnt + 1;
+endif
+
+'--- Outputs (combinational) ---
+:led    = ~led_base;
+:pin    = pin_base;
+:pin_10 = led;
+
+stop
+@enduml

UML/state.plantuml

@@ -0,0 +1,66 @@
+@startuml
+[*] --> F0 : reset/power-up
+
+state "Blink frequency\nstates" as BlinkFreq {
+  state F0
+  state F10
+  state F20
+  state F30
+  state F40
+  state F50
+}
+
+' --- Notes ---
+
+note right of F0
+  freq_idx = 0
+  f = 0 Hz (LED заморожен)
+  step_cnt считает до STEP_4SEC_MAX
+end note
+
+note right of F10
+  freq_idx = 1
+  f = 10 Hz
+  max_count = F_CLK/(2*10)-1
+  step_cnt считает до STEP_2SEC_MAX
+end note
+
+note right of F20
+  freq_idx = 2
+  f = 20 Hz
+  max_count = F_CLK/(2*20)-1
+  step_cnt считает до STEP_4SEC_MAX
+end note
+
+note right of F30
+  freq_idx = 3
+  f = 30 Hz
+  max_count = F_CLK/(2*30)-1
+  step_cnt считает до STEP_4SEC_MAX
+end note
+
+note right of F40
+  freq_idx = 4
+  f = 40 Hz
+  max_count = F_CLK/(2*40)-1
+  step_cnt считает до STEP_4SEC_MAX
+end note
+
+note right of F50
+  freq_idx = 5
+  f = 50 Hz
+  max_count = F_CLK/(2*50)-1
+  step_cnt считает до STEP_4SEC_MAX
+end note
+
+' --- Transitions ---
+
+F0  --> F10 : step_cnt >= STEP_4SEC_MAX
+F10 --> F20 : step_cnt >= STEP_2SEC_MAX
+F20 --> F30 : step_cnt >= STEP_4SEC_MAX
+F30 --> F40 : step_cnt >= STEP_4SEC_MAX
+F40 --> F50 : step_cnt >= STEP_4SEC_MAX
+F50 --> F0  : step_cnt >= STEP_4SEC_MAX
+
+F0 --> [*] : external reset
+@enduml