Programmer Interface: Data

The CTM module generates two types of event packets: trace packets and overflow packets. Trace packets contain the data traced from the processor core. 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 single trace event.

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 39 CTM Trace Packet Structure

payload word	description
0	timestamp[15:0]
1	timestamp[31:16]
2	Next Program Counter npc[15:0]
…	…
1 + ADDR_WIDTH / 16	Next Program Counter npc[ADDR_WIDTH-1:ADDR_WIDTH-16]
1 + ADDR_WIDTH / 16 + 1	Program Counter pc[15:0]
…	…
1 + 2 * (ADDR_WIDTH / 16 + 1)	Program Counter pc[ADDR_WIDTH-1:ADDR_WIDTH-16]
1 + 2 * (ADDR_WIDTH / 16 + 1) + 1	[1:0] mode: The privilege mode of the executed instruction. [2] ret: The executed instruction returned from a subroutine (e.g. Jump and Link Register (jalr) on RISC, ret on x86). [3] call: The executed instruction called a subroutine (e.g. Jump and Link (jal) on RISC, call on x86). [4] modechange: The executed instruction changed the privilege mode (e.g. from user to kernel space). [15:5] reserved

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 40 CTM Overflow Packet Structure

payload word	description
0	number of missed events