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Serial communication protocols
Deployment - Modbus > Modbus - Function codes
5.6.3 Modbus - Function codes
Naming convention
Range definitions
82
3.
Evaluate respond telegram
3. slave:
...
A request may be sent to a specified slave or as broadcast telegram to all slaves. To
mark a broadcast telegram the slave address is set to 0.
Only write commands may be sent as broadcast.
After a broadcast the master is not waiting for a respond telegram.
Modbus has some naming conventions:
Modbus differentiates between bit and word access; bits = "Coils" and words = "Reg-
n
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
VIPA System SLIO
HB300 | CP | 040-1CA00 | en | 18-28
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