At one time, printers used a form of a CR/LF protocol.
A printer protocol is data dump on a periodic basis, every time interval or on host demand/command .
The periodic basis time interval is not consistent with Modbus because Modbus is a master/slave protocol where the master requests data and the slave replies with the data. A device that spits out data on a periodic basis pays no attention to a Modbus master request.
Modbus was designed for dealing with quasi-realtime data, the most recent data value. Although there are a couple Modbus Function Codes that deal with transferring blocks of data, like a set of historical values, there are very few, if any, Modbus devices (Masters or slaves) that implement those Function Codes.
So the prospect of a Master requesting data from the past 5 minutes or past hour does not have a high probability of success.
I suspect that you need a custom algorithm to capture periodic bursts of data from whatever it is that is generating the data using a CR/LF protocol.