Siemens SINAMICS G120 Instructions d'exploitation Page 141

  • Télécharger
  • Ajouter à mon manuel
  • Imprimer
  • Page
    / 304
  • Table des matières
  • MARQUE LIVRES
  • Noté. / 5. Basé sur avis des utilisateurs
Vue de la page 140
Configuring the fieldbus
6.2 Communication via RS485
Inverter with CU240B-2 and CU240E-2 Control Units
Operating Instructions, 01/2011, FW 4.4, A5E02299792B AB
139
6.2.3.3 Modbus RTU telegram
Description
For Modbus, there is precisely one master and up to 247 slaves. Communication is always
triggered by the master. The slaves can only transfer data at the request of the master.
Slave-to-slave communication is not possible. The Control Unit always operates as slave.
The following figure shows the structure of a Modbus RTU telegram.
Character delay time
Character delay time
Character delay time
Character delay time
Character delay time
Character delay time
≥ 3.5 bytes
≥ 3.5 bytes
Initial pause Interframe
delay
Function
code
Data
Initial
pause
Interframe
delay
Interframe
delay
End pause
Slave
1 Byte
1 Byte 1 Byte 1 Byte 1 Byte 1 Byte 1 Byte
CRC low CRC high
1 Byte 0 ... 252 Bytes
2 Byte
CRC
3URWRFRO'DWD8QLW3'8
$SSOLNDWLRQ'DWD8QLW0RGEXVIUDPH
0RGEXV5787HOHJUDPP
$SSOLNDWLRQ'DWD8QLW
0RGEXVIUDPH
$SSOLNDWLRQ'DWD8QLW
0RGEXVIUDPH
Figure 6-12 Modbus with delay times
The data area of the telegram is structured according to the mapping tables.
Vue de la page 140
1 2 ... 136 137 138 139 140 141 142 143 144 145 146 ... 303 304

Commentaires sur ces manuels

Pas de commentaire