7.7 Modbus - Function codes
Modbus has some naming conventions:
n
Modbus differentiates between bit and word access; bits = "Coils" and words = "Reg-
ister".
n
Bit inputs are referred to as "Input-Status" and bit outputs as "Coil-Status".
n
word inputs are referred to as "Input-Register" and word outputs as "Holding-Reg-
ister".
Normally the access at Modbus happens by means of the ranges 0x, 1x, 3x and 4x.
0x and 1x gives you access to digital bit areas and 3x and 4x to analog word areas.
For the CPs from VIPA is not differentiating digital and analog data, the following assign-
ment is valid:
0x - Bit area for master output data
Access via function code 01h, 05h, 0Fh
1x - Bit area for master input data
Access via function code 02h
3x - word area for master input data
Access via function code 04h
4x - word area for master output data
Access via function code 03h, 06h, 10h
A description of the function codes follows below.
With the following Modbus function codes a Modbus master can access a Modbus slave:
With the following Modbus function codes a Modbus master can access a Modbus slave.
The description always takes place from the point of view of the master:
Naming convention
Range definitions
Overview
VIPA System 300S
+
Deployment PtP communication
Modbus - Function codes
HB140 | CPU-SC | 313-5BF23 | en | 19-01
163
