System Architecture

Implementation Aspects

Overflow Handling

Todo

make this a bit less vague and about the future, but about what we have now.

In case the trace events are generated at a faster rate than the host interface can transfer. This problem becomes crucial with the increasing number of trace modules. Generally, this can be done on the level of the debug system by a sophisticated flow control that will be specified in later revisions. An overflow occurs if a trace event is generated, but cannot be transferred or buffered due to backpressure from the interconnect, but backpressure cannot be generated to the system module. In the current specification the trace infrastructure detects this situation, counts how many packets could not be transfered and then transfers a missed_events event once it the interface is available again.

Clock and Power Domains

Todo

copy clock and power domain aspects from architecture doc

Physical Interfaces

Note

This version of the Open SoC Debug specification does not describe any physical interface.

Todo

leave this out of the spec!? or put it next to HIM?

The physical interface is abstracted in Open SoC Debug as a FIFOs which transmit data between the host and the device.

Fig. 5 GLIP as abstraction layer from the physical interface

While not required by OSD, we recommend building on top of GLIP as depicted in @fig:glip_overview. GLIP provides a generic FIFO interface that reliably transfers data between the host and the system. Multiple alternatives for simulations and prototyping hardware exist. In a silicon device, a high-speed serial interface is most probably favorable.