It is my understanding the Modbus map has historical data up to the last five events but no SER/SOE data with timestamps. Is there any way to bring timestamp information via Modbus even though Modbus natively does not support timestamp?

 

Standard modbus doesn't usually support transmitting history. I have seen some slave devices that include data from the last 15 days or so in a standard modbus map. The data is not timestamped. The location defines the time period. For eg. 40001 = yesterdays value, 40002 = the day before etc.

History through modbus is usually done using Enron modbus. There is an explanation on how this works at http://www.simplymodbus.ca/Enron.htm

Enron date timestamps are two 32 bit floats for date and time in the format 092206.0 for Sep 22,2006 and 142645.0 for 2:26:45 pm
I've seen many other ways to format date and time as well. It is up to the manufacturer on how they want to define it in the map.