Command Code And Communication Data Illustration; Rtu Mode - INVT Goodrive20-EU VFD Series Operation Manual

Goodrive20-EU series VFD
DATA (N-1)
...
DATA (0)
LRC CHK Hi
LRC CHK Lo
END Hi
END Lo
7.2.3.1 ASCII mode check (LRC Check)
Check code (LRC Check) is the value combined of address and data content result. For
instance, the
0x02+0x06+0x00+0x08+0x13+0x88=0xAB, then take the compliment of 2=0x55. Below is a
simple LRC calculation function for user reference (programed with C language):
Static unsigned char
LRC(auchMsg,usDataLen)
unsigned char *auchMsg;
unsigned short usDataLen;
{
unsigned char uchLRC=0;
while(usDataLen--)
uchLRC+=*auchMsg++;
return((unsigned char)( – ((char)uchLRC)));
}

7.3 Command code and communication data illustration

7.3.1 RTU mode

7.3.1.1 Command code: 03H
03H (correspond to binary 0000 0011) ,read N words (Word) (N≤16)
Command code 03H means that if the master read data from the VFD, the data number
depends on the "data number" in the command code. The max. number is 16 and the
parameter address to be read must be continuous. The length of every data is 2 bytes (one
word). The following command format is illustrated in hex (a number with "H" means hex) and
one hex number occupies one byte.
This command code is used to read the working state of the VFD.
For example, read continuous 2 data content from0004H from the VFD with the address of
01H (read the content of data address of 0004H and 0005H), the frame structure is as follows:
RTU master command message (from the master to the VFD)
nx8-bit data content is formed by combination of 2n (n≤16)
8-bit check code is formed by the combination of two ASCII
check code of
Data content:
ASCII codes
LRC check code:
codes.
End character:
END Hi=CR (0x0D), END Lo=LF (0x0A)
above 2.2.2
120
Communication protocol
communication message is: