A multi-resolution AHB bus tracer for real-time compression of forward/backward traces in a circular buffer

The forward/backward trace refers to the trace captured after/before a target point is reached, respectively. Real time compression of the backward trace in a circular buffer is a challenging problem since the initial state of the trace currently under compression might be overwritten when wrapping around occurs. This paper presents a real time multi-resolution AHB on-chip bus tracer which is capable of capturing and compressing both forward and backward traces in a circular buffer. The backward trace is accomplished with a ping-pong organization of dual forward trace compression engines. While one module is compressing the trace, the other is clearing up its internal data structure. The roles of the two engines are exchanged periodically. The Bus Tracer, costs 60 K gates and runs up to 500 MHz in TSMC 0.13 mum technology. The experiments show that our approach achieves 2.32 to 3.98 times in effective trace depth than traditional circular buffer approaches.