Programmer Interface: Data¶

The STM module generates two types of event packets: trace packets and overflow packets. Trace packets contain the trace data in the form of (id,value) tuples. Overflow packets indicate that trace events were missed, usually if more events are generated than the module can send out to the DI.

Trace Packets¶

A Trace Packet encapsulates a trace event, which consists of an identifier id (always 16 bit wide) and an associated value value (VALWIDTH bit wide).

The following fields in the header of the DI packet are set:

FLAGS.TYPE is set to EVENT
FLAGS.TYPE_SUB is set to 0

Table 31 STM Trace Packet Structure¶
payload word	description
0	`timestamp[15:0]`
1	`timestamp[31:16]`
2	`id`
3	`value[15:0]`
…	…
2 + `VALWIDTH` / 16	`value[VALWIDTH-1:VALWIDTH-16]`

Overflow Packets¶

The following fields in the header of the DI packet are set:

FLAGS.TYPE is set to EVENT
FLAGS.TYPE_SUB is set to 0x5

Table 32 STM Overflow Packet Structure¶
payload word	description
0	number of missed events