[PDF] Specification and Implementation Guide for MODBUS over Two-Wire interface is the most common. As an add-on option, RS485 Four-Wire interface may also be implemented. 2.4 Master / Slaves State Diagrams The MODBUS data link layer comprises two separate sub layers : The RTU and ASCII transmission modes are specified in next chapters using two state diagrams. The reception and the sending of a Wiring Diagrams | York - Johnson Controls DISCLAIMER. This material is for professional use only and is intended to be used only as reference material by licensed contractors when installing or servicing Reznor equipment. Nortek Global HVAC/Reznor does not endorse any field changes to factory wiring schemes. AAON RN Series Installation, Operation & Maintanance Manual View and Download AAON RN Series installation, operation & maintanance manual online. Packaged Rooftop Units, Heat Pumps, & Outdoor Air Handling Units. RN Series Heat Pump pdf manual download.