Logic Analyzer core: Trigger Sequence States

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Trigger Sequence States

Sequence states allow you to control how the analyzer evaluates and stores sampled data. Each state gives you control over data capturing, searching for a target (optionally multiple times), or branching to another sequence should a special condition occur. On a hit, the analyzer advances to the next sequence state. It can also trigger the analyzer controller & start/stop timers. With 16 sequence states, you can create complex protocol following triggers.

Figure 24 - Example Sequence Level For each state you specify:

• Capture Term (sum of trigger terms, range checks, edge detect & timer hits) • Hit Term (sum of trigger terms, range checks, edge detect & timer hits) • Else Term (sum of trigger terms, range checks, edge detect & timer hits) • Occurrence Count • Else State • Timer Control Flags (start/stop/clear for timers 1 & 2) • Trigger Flag

The trigger sequencer itself is a relatively simple state machine. Pseudocode for it is:

if (sampled_input valid) then {

   if (capture_term valid) then
       capture data

   if (hit_term valid) then {
       increment hit_count
       if (hit_count == fsm_occurence_count) then {    
           update_timers
           reset hit_count
           if (fsm_trigger || last_state) then assert run to controller
           if (!last_state && !fsm_last_state) advance to next state
       }
   }

   otherwise if (else_term valid) then {
       reset hit_count
       go to state "fsm_else_level"
   }

}

Figure 25 - Trigger Sequencer State Machine

8.1 Example (Trigger Sequence Initialization)

1. define TRIGSTATE_STATENUM_MASK 0xF
2. define TRIGSTATE_OBTAIN_MASK 0x000FFFFF
3. define TRIGSTATE_ELSE_BITOFS 20
4. define TRIGSTATE_STOP_TIMER0 0x01000000
5. define TRIGSTATE_STOP_TIMER1 0x02000000
6. define TRIGSTATE_CLEAR_TIMER0 0x04000000
7. define TRIGSTATE_CLEAR_TIMER1 0x08000000
8. define TRIGSTATE_START_TIMER0 0x10000000
9. define TRIGSTATE_START_TIMER1 0x20000000
10. define TRIGSTATE_TRIGGER_FLAG 0x40000000
11. define TRIGSTATE_LASTSTATE 0x80000000

void write_trigger_state (

 int statenum,     // 0 to 15
 int last_state,
 int set_trigger,
 int start_timer,  // bit0=timer1, bit1=timer2
 int stop_timer,   // bit0=timer1, bit1=timer2
 int clear_timer,  // bit0=timer1, bit1=timer2
 int else_state,   // 0 to 15
 int obtain_count)

{

 write_select (statenum & TRIGSTATE_STATENUM_MASK);

 unsigned int value =
   ((else_state & TRIGSTATE_STATENUM_MASK)<<TRIGSTATE_ELSE_BITOFS) |
   (obtain_count & TRIGSTATE_OBTAIN_MASK);
 if (last_state) value |= TRIGGER_LASTSTATE;
 if (set_trigger) value |= TRIGSTATE_TRIGGER_FLAG;
 if (start_timer & 1) value |= TRIGSTATE_START_TIMER0;
 if (start_timer & 2) value |= TRIGSTATE_START_TIMER1;
 if (stop_timer & 1) value |= TRIGSTATE_STOP_TIMER0;
 if (stop_timer & 2) value |= TRIGSTATE_STOP_TIMER1;
 if (clear_timer & 1) value |= TRIGSTATE_CLEAR_TIMER0;
 if (clear_timer & 2) value |= TRIGSTATE_CLEAR_TIMER1;
 write_chain (value);

}

Figure 26 - Initialize Trigger Sequence