The RS-485 Modbus RTU connection between a Honeywell XYR 5000 base station (Modbus slave)and a Honeywell Trendview recorder (Modbus Master) requires that the turn around time setting for the RS-485 on the Trendview recorder be 1mS, not the default 3mS.  

Experience shows that the default 3mS setting gets less than 1% of the responses from the XYR base station; producing a very intermittent, fault and error prone Modbus link.   The 1mS setting runs perfectly, with zero errors.

Budd