Goodrive100 inverters
Communication protocol
IKR Aandrijven en Besturen
www.ikr-industries.nl
CRC CHK high bit
END
T1-T2-T3-T4(transmission time of 3.5 bytes)
9.3.2.1 RTU communication frame error checkout
Various factors (such as electromagnetic interference) may cause error in the data transmission. For
example, if the sending message is a logic “1”,A-B potential difference on RS485 should be 6V, but in
reality, it may be -6V because of electromagnetic interference, and then the other devices take the sent
message as logic
“
0
”
. If there is no error checkout, the receiving devices will not find the message is
wrong and they may give incorrect response which cause serious result. So the checkout is essential to the
message.
The theme of checkout is that: the sender calculate the sending data according to a fixed formula, and then
send the result with the message. When the receiver gets this message, they will calculate anther result
according to the same method and compare it with the sending one. If two results are the same, the
message is correct. If not, the message is incorrect.
The error checkout of the frame can be divided into two parts: the bit checkout of the byte and the whole data
checkout of the frame (CRC check).
Bit checkout of the byte
The user can select different bit checkouts or non-checkout, which impacts the check bit setting of each byte.
The definition of even checkout: add an even check bit before the data transmission to illustrate the number of
“1” in the data transmission is odd number or even number. When it is even, the check byte is “0”, otherwise,
the check byte is”1”. This method is used to stabilize the parity of the data.
The definition of odd checkout: add an odd check bit before the data transmission to illustrate the number of
“1” in the data transmission is odd number or even number. When it is odd, the check byte is “0”, otherwise,
the check byte is”1”. This method is used to stabilize the parity of the data.
For example, when transmitting “11001110”, there are five “1” in the data. If the even checkout is applied, the
even check bit is “1”; if the odd checkout is applied; the odd check bit is “0”. The even and odd check bit is
calculated on the check bit position of the frame. And the receiving devices also carry out even and odd
