Frequency Converter Address (Adr); Data Control Byte (Bcc); The Data Field - Danfoss VLT AQUA Drive FC 202 Design Manual

RS-485 Installation and Set...

7.4.4 Frequency Converter Address (ADR)

Two different address formats are used.
The address range of the frequency converter is either 1–
31 or 1–126.
1. Address format 1–31:
Bit 7=0 (address format 1–31 active)
Bit 6 is not used
Bit 5=1: Broadcast, address bits (0–4) are not used
Bit 5=0: No Broadcast
Bit 0–4=frequency converter address 1–31

7.4.6 The Data Field

The structure of data blocks depends on the type of telegram. There are 3 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 7.7 PCD
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 7.8 Parameter Block
Text block
The text block is used to read or write texts via the data block.
STX LGE ADR PKE
Illustration 7.9 Text Block
MG20Z202
Design Guide
PCD1
PWE
PKE IND
high
IND Ch1 Ch2
Danfoss A/S © Rev. 06/2014 All rights reserved.
2. Address format 1–126:
Bit 7=1 (address format 1–126 active)
Bit 0–6=frequency converter address 1–126
Bit 0–6=0 Broadcast
The follower returns the address byte unchanged to the
master in the response telegram.

7.4.5 Data Control Byte (BCC)

The checksum is calculated as an XOR-function. Before the
first byte in the telegram is received, the Calculated
Checksum is 0.
PCD2
PWE
PCD1
low
Chn PCD1
BCC
PCD2 BCC
PCD2 BCC
151
7 7