Appendix C: Modbus Protocol Implementation Conformance Statement
RTU Open v3
Carrier Proprietary and Confidential
CARRIER CORPORATION ©2016
Integration Guide
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47
Date: 11/12/2013
Vendor Name:
Carrier
Product Names:
RTU Open
Product Model Number:
RTU Open
Protocol Description:
The RTU Open controller speaks the Modicon Modbus RTU/ASCII Protocol as described in the
Modicon Modbus
Protocol Reference Guide, PI-MBUS-300 Rev.J.
Further details on the Modbus implementation are described
below.
Product Description:
The RTU Open is a factory-installed rooftop controller that is capable of speaking multiple protocols.
Serial Transmission Mode:
Supported?
RTU
Slave only
ASCII
Not supported
Communication
Types:
Baud rates:
Data Bits:
Parity:
Stop Bits:
2-wire EIA-485,
9600, 19200,
38400, 76800
8
None
1
Function Codes:
Purpose:
Used with Register
Numbers:
01 – Read Coil Status
Read Discrete Outputs
00001 - 65535
02 – Read Input Status
Read Discrete Inputs
00001 - 65535
03 – Read Holding Registers
Read Holding Registers
00001 - 65535
04 – Read Input Registers
Read Input Registers
00001 - 65535
05 – Force Single Coil
Write Discrete Outputs (single)
00001 - 65535
06 – Preset Single Register
Write Holding Registers (single)
00001 - 65535
15 – Force Multiple Coils
Write Discrete Outputs
00001 - 65535
16 – Preset Multiple Coils
Write Holding Registers
00001 - 65535
Register Type:
Range:
Function Codes Used with this
Register Type:
Float Value (FLOAT)
Single-Precision IEEE floating point
value
3 – Read Holding Register
6 – Preset Single Register
16 – Preset Multiple Register
Appendix C: Modbus Protocol Implementation Conformance Statement