The Data Field - Danfoss FC 101 Design Manual

RS-485 Installation and Set...

7.4.6 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 7.5 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 7.6 Parameter Block
Text block
The text block is used to read or write texts via the data block.
STX LGE ADR PKE
Illustration 7.7 Text Block
®
VLT HVAC Basic Drive FC 101 Design Guide
PCD1
PWE
PKE IND
high
IND Ch1 Ch2
MG18C502 - Rev. 2013-09-06
PCD2
PWE
PCD1
low
Chn PCD1
BCC
PCD2 BCC
PCD2 BCC
83
7 7