The Data Field - Danfoss VLT AutomationDrive FC 301 Design Manual

RS-485 Installation and Set...

12.7.6 The Data Field

The structure of data blocks depends on the type of telegram. There are 3 telegram types, and the type applies for both
control telegrams (master⇒follower) and response telegrams (follower⇒master).
The 3 types of telegram are:
Process block (PCD)
The PCD is made up of a data block of 4 bytes (2 words) and contains:
•
Control word and reference value (from master to follower)
•
Status word and present output frequency (from follower to master)
STX LGE ADR
Illustration 12.7 Process Block
Parameter block
The parameter block is used to transfer parameters between master and follower. The data block is made up of 12 bytes (6
words) and also contains the process block.
STX LGE ADR
Illustration 12.8 Parameter Block
Text block
The text block is used to read or write texts via the data block.
STX LGE ADR PKE
Illustration 12.9 Text Block
®
VLT AutomationDrive FC 301/FC 302 Design Guide, 0.25-75 kW
PCD1
PWE
PKE IND
high
IND Ch1 Ch2
MG33BF02 - Rev. 2013-12-20
PCD2
PWE
PCD1
low
Chn PCD1
BCC
PCD2 BCC
PCD2 BCC
179
12 12