The User Manual of JAC200 Series General Frequency Converter
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Field description for data frame:
Frame header
START
Idle longer than 3.5 characters transmission time
Slave machine
ADR
Correspondence address range: 1 ~247 ; 0 =broadcast address
Command code
CMD
03: read slave machine parameter; 06: write slave machine parameter
Function code
address H
The internal parameter address for the frequency converter, it is shown by
hexadecimal; divided into the function code type and non-function code type (such
as running parameters, run command, and so on) parameters, etc. See the address
definition for more details.
When transmitting, the high byte is in front and the low byte is behind.
Function code
address L
Function code
number H
Function code number read for the frame, if it is 1, it indicates 1 function code.
When transmitting, the high byte is front and the low byte is behind.
This protocol can only rewrite 1 function code for one time, and doesn’t have this
field.
Function code
number L
Data H
Respondent data or waiting-to-be written data, when transmitting, the high byte is
front and the low byte is behind.
Data L
CRC CHK high
position
Detection value: CRC16 proof test value. When transmitting, the high byte is front
and the low byte is behind.
See the instruction of CRC verification in this section for the detailed computing
method
CRC CHK low
position
END
When there are 3.5 characters
CRC verification mode:
CRC
（
Cyclical Redundancy Check
）
uses the RTU frame format, and the includes the error detection
domain based on CRC method. CRC domain detects the contents of the whole messages. CRC domain is
two bytes, including 16 digit binary values. It is added into the message after the calculation by the
transmission equipment. The receiving equipment recalculates the CRC that receives the message, and
makes a comparison to the value in the received CRC domain. Whether the two CRC values are not equal,
then it indicates the transmission errors. As for CRC, 0xFFFF is stored first, and then call a procedure to
treat the continuous 8-bit bytes in the message and the value in the current register. Only the 8Bit data in
each character is valid to CRC, while the start bit and stop bit as well as the parity check bit are all invalid.
During the production of CRC, each 8-digit byte alone is different from the content in the register, or
(XOR), the result is the action toward the direction of least significant bit, and the most significant bit is
filled with 0. LSB is detected by extracting out, whether the LSB is 1, then the separate value and the preset
value in the register are different or, whether the LSB is 0, then no operation is conducted. The whole
