A CSM is constructed using the following STP message primitives:
- A header word (32-bit STP data word)
- One or two counter valid words (32-bit STP data word) that indicate which counters are active and included in the message frame
- One or two counter overflow words (32-bit STP data word) that indicate which of the counters have wrapped since the last message frame
- Overflow export is an optional feature
- One or more counter value words (32-bit STP data word) that contain the counter values for every counter designated for export
- The final write has a timestamp to mark the end of the message frame. The final data is still D32
- On ATB interface this message will be bounded by a global timestamp and the timestamp value, and will be based on STP 2.0
Figure 13-5 shows the CSM message format.