Rs-485 Multi-Drop Configuration - Honeywell CIU 888 Protocol Manual

FIGURE 1-7
Part No.: 4417589_Rev13
CIU Emulation

1.3.2 RS-485 multi-drop configuration

In case of an RS-485 multi-drop setup, there is a restriction in the use of
RTU addresses. For example, RTU addresses 32 and 42 for two
CIU 888s connected to the same RS-485 line will malfunction, while
RTU addresses 32 and 34 will work properly (see FIGURE 1-7).
Schematic representation of the handling of request and reply between a host system
and gauges underneath a downlink CIU in RS-485 multi-drop configuration
Protocol Manual - CIU Emulation
CIU 888 1 - 9