Operating Instructions

Chapter 4 - Parameters and Menu Structure
I/O and Hardware (M5)
147 | 187
Siemens Industry, Inc.
Siemens BT300 HVAC Drive
DPD01809
Smart Infrastructure
2019-05-29
Slave device failure (P5.8.3.2.8)
An unrecoverable error occurred while the server (or slave) was attempting to perform the requested action.
Last fault response (P5.8.3.2.9)
Displays the last fault response as Fault code.
Control word (P5.8.3.2.10)
Displays the Control Word received from the bus.
Word status (P5.8.3.2.11)
Displays the current Status Word that is sent to the bus.
Communications
Features of the Modbus-Siemens interface:
● Direct control of the Siemens drive (for example, Run, Stop, Direction, Speed reference, Fault reset)
● Full access to all Siemens parameters
● Monitor the Siemens status (Output frequency, Output current, Fault code)
Data addresses in Modbus messages
All data addresses in Modbus messages are referenced to zero. The first occurrence of a data item is
addressed as item number zero. For example:
● The coil known as Coil 1 in a programmable controller is addressed as Coil 0000 in the data address field
of a Modbus message.
● Coil 127 decimal is addressed as Coil 007E hex (126 decimal).
● Holding register 40001 is addressed as register 0000 in the data address field of the message. The
function code field already specifies a ‘holding register’ operation. Therefore the 4XXXX reference is
implicit.
● Holding register 40108 is addressed as register 006B hex (107 decimal).
Modbus Memory Map
The Siemens variables and fault codes as well as the parameters can be read and written from Modbus. The
parameter addresses are determined in the application. Every parameter and actual value has been given an
ID number in the application. The ID numbering of the parameter as well as the parameter ranges and steps
can be found in the operator's manual in question. The parameter value shall be given without decimals. If
several parameters/actual values are read with one message, the addresses of the parameters/actual values
must be consecutive.
Table 109: Supported Modbus Functions.
Function
Code
Modbus Function Name
TCP/RTU
Access
Type
Address Range
(hex)
1 (0X01)
Read coils
TCP only
Discrete
00000 - 0FFFF
2 (0X02)
Read Discrete Inputs
TCP only
Discrete
10000 - 1FFFF
3 (0X03)
Read Holding Registers
TCP&RTU
16bit
40000 - 4FFFF
4 (0X04)
Read Input Registers
TCP&RTU
16bit
30000 - 3FFFF
5 (0X05)
Write Single Coils
TCP only
Discrete
00000 - 0FFFF