MTB specifics

The ARM Micro Trace Buffer (MTB) is an on-chip trace buffer that allows to do post-mortem instruction trace via a regular J-Link with no need of a specific J-Trace unit. The MTB will use a specific amount of the on-chip RAM to store trace data while the core executes instructions. MTB is mainly used on smaller MCUs like Cortex-M0+/M23/M33 based ones.

Limitations

MTB is a very limited version of trace that has the following limitations:

• Instruction trace support only
• No streaming trace possible
• A portion of the target RAM may not be used by the application if MTB is used

Configuration options provided by J-Link

An MTB consists of the following registers / bit fields that allow configuration of the MTB and the amount of RAM it uses:

 // MTB_BASE           32-bit register that specifies the base address of the MTB buffer
 // MTB_POINTER        32-bit register that specifies the offset (rel. to BASE) where the next trace packet will be stored by the HW
 // MTB_MASTER.MASK    5-bit bitfield that specifies the wrap-around point for the auto-inc logic of the MTB, on packet store