Veichi AC90 Manual page 187

AC90 TENSION CONTROL FREQUENCY INVERTER MANUAL
RTU Host machine command information
START
Slave machine address
Command code
Detecting code high-order
Detecting code low-order
Data high-order
Data low-order
CRC CHK low-order
CRC CHK high-order
END
RTU Slave machine responding information（normal）
START
Slave machine address
Command code
Detecting code high-order
Detecting code low-order
Data high-order
Data low-order
CRC CHK low-order
CRC CHK high-order
END
RTU Slave machine responding information（abnormal）
START
slave machine address
Command code
Error code
CRC CHK low-order
CRC CHK high-order
END
Communication frame error check mode
The standard ModBus serial network adopts two kinds of error check mode: odd/even checking which is used to check
every character and CRC detecting which is used to check one frame of data.
1. Odd-even checking
The users can configure the controller with odd or even checking, or no checking, what will determine how to set
odd/even checking in every character.
If odd /even checking have been allocated, "1" bit will be accounted to the bit number of each character (7 bits in ASCII
mode, 8 bits in RTU). For instance, the RTU character frame contains the following 8 bits: 1 1 0 0 0 1 0 1
There are 4 bits with number"1". If using the even checking, odd/even checking bit of the frame will be 0, then there are
still 4 bits with number"1". If using odd checking, odd/even checking bit of the frame will be 1, then there are 5 bits with
number"1".
BASIC OPERATION AND TRIAL RUN
Transmission time of 3.5 bytes
01H
08H
00H
00H
13H
88H
EDH
5DH
Transmission time of 3.5 bytes
Transmission time of 3.5 bytes
01H
08H
00H
00H
13H
88H
EDH
5DH
Transmission time of 3.5 bytes
Transmission time of 3.5 bytes
01H
88H
03H
06H
01H
Transmission time of 3.5 bytes
182