Reporter :PCLee

The decisions on when to acquire debug data during post-silicon validation are determined by trigger events that are programmed into on-chip trigger units. In this paper, we investigate how to design trigger units that are both resource-efficient and runtime programmable. To achieve these two goals, we introduce new architectural features, as well as an algorithm for automatically mapping trigger events onto trigger units.

[2, 3] scan-based post silicon validation This paper Provide real-time observability [4] on-chip trace buffer [5] embedded breakpoint units [6] on-chip programmable trigger engines Improve the control on trace buffer, and reduce the amount of data Achieve resource –efficient and revert the false decision in real time

What’s the problem:  For a chip, we can only configure their register. How many trigger units we need?  How to reduce the number of trigger units to save area?  How to recover our data from false trigger?

Trigger unit TS = xx10 => output = 1 (x is don’t care)  event_reg = 0010  mask = ≤ TS ≤ 5 => ABCD = (0010, 0011, 0100, 0101) => TS = A’BC’ + A’B’C => mask1 = 1110 event_reg1 = 0100 mask2 = 1110 event_reg2 = 0010 AB/ CD

2 ≤ TS ≤ 5 and TS = 10 => ABCD = (0010, 0011, 0100, 0101, 1010) 1. Add one more quality unit. 2. Under trigger => TS = A’BC’ + A’B’C + B’CD’ => mask1 = 1110 event_reg1 = 0100 mask2 = 1110 event_reg2 = 0010 mask3 = 0111 event_reg3 = 0010 => We need 3 trigger units to cover all conditions. => If we have k terms, we need k units. Problem: If we just have 2 trigger units? (If we don’t have enough trigger units to cover all conditions?) AB/ CD

Under-triggering:  Configure register next time to cover all conditions.  It cannot work on asynchronous peripherals Over-triggering: => TS = A’BC’ + B’C => mask1 = 1110 event_reg1 = 0100 mask2 = 0110 event_reg2 = 0010 AB/ CD F 1011 Off-prime will cause false triggering

Debug flow 1. Off-primes are computed Off-line. 2. Configure events to register and off-primes to trace buffer. 3. When events have been triggered, trace buffer starts trace data. And event buffers starts to record TS. 4. Event buffers compare off-sets sequentially. 5. When it found false-triggering, mark the segment of trace buffer for further reuse. Problem:  If the number off-primes is larger than the clock cycles between consecutive events, analysis data will miss.  Add more buffers will affect the area. So this paper introduce algorithm for saving the area. m=2

Purpose:  Prevent early filling of event buffers.  Prevent loss valid trigger events.  Ensure trigger analysis can be done in a low number of clock cycles. iterative until gain is highest Perform minimization Revert choice Record off-prime and replace Perform minimization and return off-primes and value of mask and event register/

The obvious different is if we use event sequencing or not.  Because event buffer will have groups in event sequencing.

Conclusion of this paper  This paper map the user-programmable trigger conditions onto a lower number.  The proposed algorithm found off-prime and than revert the false triggering. My conclusion  How does this paper know the clock cycles between two events.  This paper present resource-efficient algorithm and architecture. I can reference this paper for my reconfigurable hardware.